Tiny system font size disaster

A lot said, but little meaning as a response to me. All you're proving is that you can read the contents of a link. Is your point this line?

You can’t remove or disable system fonts.

From within Font Book, no. It won't let you. Nor manually from the desktop if System Integrity Protection is enabled. That doesn't mean it's impossible. None of the following are in my /System/Library/Fonts/ folder. I removed them.

Apple Braille Outline 6 Dot.ttf

Apple Braille Outline 8 Dot.ttf

Apple Braille Pinpoint 6 Dot.ttf

Apple Braille Pinpoint 8 Dot.ttf

Apple Symbols.ttc

AppleSDGothicNeo.ttc

AquaKana.ttc

Avenir Next Condensed.ttc

Avenir Next.ttc

GeezaPro.ttc

Hiragino Sans GB W3.ttc

Hiragino Sans GB W6.ttc

Kohinoor.ttc

KohinoorBangla.ttc

KohinoorTelugu.ttc

MarkerFelt.ttc

Noteworthy.ttc

Optima.ttc

Palatino.ttc

STHeiti Light.ttc

STHeiti Medium.ttc

STHeiti Thin.ttc

STHeiti UltraLight.ttc

Thonburi.ttc

ヒラギノ明朝 ProN W3.ttc

ヒラギノ明朝 ProN W6.ttc

ヒラギノ角ゴシック W0.ttc

ヒラギノ角ゴシック W1.ttc

ヒラギノ角ゴシック W2.ttc

ヒラギノ角ゴシック W3.ttc

ヒラギノ角ゴシック W4.ttc

ヒラギノ角ゴシック W5.ttc

ヒラギノ角ゴシック W6.ttc

ヒラギノ角ゴシック W7.ttc

ヒラギノ角ゴシック W8.ttc

ヒラギノ角ゴシック W9.ttc

Are you trying to disable SIP by terminal command and trying to delete the fonts and that is not recommended.

No, not trying. I'm succeeding. And quite intentionally. "Recommended" isn't the same as "your computer will explode if you remove a font the OS installs".

Apparently, you've never worked in prepress, where the goal (for most such users) is to keep all unnecessary fonts off of your computers at all times. You will have far fewer font conflict issues with the fonts customers send you to use with their projects.

That basic premise is the entire point of my article. You might want to give it a read.

Font Management in macOS and OS X

I may receive some form of compensation, financial or otherwise, from my recommendation or link.

Red normally indicates a more than passing flaw with the font. It should be removed and replaced with a fresh copy. Yellow symbols can be ignored virtually 100% of the time. Without having access to the font, I can't guess how it's seeing a duplicate within the font's structure.

Tahoma is an OS supplied font. Actually, it's a Microsoft font supplied to Apple for use in the OS. Office for Mac will also install this font set.

Tahoma is fine on my end, so something about your copies are damaged enough that the OS thinks the regular and negreta (bold) versions are conflicting with each other. Pull clean copies from a backup and replace both Tahoma.ttf and Tahoma Bold.ttf in the /Library/Fonts/ folder. You can also use Pacifist to extract clean copies from the El Capitan .dmg installer.

MT Extra is a font installed by MS Office for Mac. Replace that one also with a clean copy.

Did you look in the "purchased" column of Appstore?

After download it is in the Applications folder, then move it somewhere else to keep. Even if the signature might be gone, you always can extract files from it with Pacifist.

Kurt, do you suggest that I just trash MT Extra from within the FontBook app?

Unless it's a font you need for its special characters, just trash it.

Normal (flagged as duplicate) /library/fonts/tahoma.ttf

Regular /users/username/library/fonts/tahoma (without extension)

Bold /users/username/library/fonts/tahoma (without extension)

Negreta (flagged as duplicate) /library/fonts/tahoma bold.ttf

Aha! There's the cause of the duplicate flags in Font Book. The two without an extension are much older OS 9 style TrueType fonts. They're conflicting not only with the newer .ttf OpenType versions, but with each other. Delete those two older versions so only the two .ttf versions remain.

TypeBook flags the older versions without extensions as being the good ones. If I click through to individually manually correct these files, it shows me the .ttf version in Finder.

It doesn't have anything to do with which ones are "good". Unix defines the order of Fonts folder importance as follows:

~/Library/Fonts/ (the active user account)

/Library/Fonts/

/Network/Library/Fonts/

/System/Library/Fonts/

/System Folder/Fonts/ (the OS 9 Fonts folder)

You would think the System folder's fonts would get top billing, but they don't. Which seems very backwards to me, but that's the way it is. It's also how the Lucida Grande hack works. Because the altered fonts are placed in your user account, they are used ahead of the real San Francisco fonts, despite both being active. This folder weight order is the only reason Font Book is marking the older versions green, and the newer versions as a problem.

Both versions of Tahoma were created by Microsoft. Both have the same internal names. The way to get it right is to remove those much older versions from the drive. They're not only really old, but the two copies that have no extension are identical to each other. A legacy Mac TrueType font is a suitcase. They both contain Tahoma and Tahoma Bold. The .ttc versions are separated as individual fonts.

It appears from this (and probably also applicable to the remaining 43 problems) that the OS does not properly remove fonts by trashing the apps which installed them.

How is what another app installs Apple's fault? All the way up to Office for Mac 2011, MS was still installing a bunch of OS 9 legacy TrueType font files (62 of them). Not that it's a terrible thing to do that since you can still use them, but a handful conflict with the greatly newer .ttf and .ttc versions installed by they OS. That's simply sloppy programming by MS to insist on continually installing fonts they should darn well know will conflict with the newer OS installed versions that already exist. Anytime a user installs Office 2008 or 2011, it will install these ancient conflicting fonts:

Andale Mono

Arial Black

Arial Narrow

Arial Rounded Bold

Comic Sans MS

Georgia

Impact

Tahoma

Trebuchet MS

Notice Tahoma is one of them. All of these older versions without an extension should be deleted from the drive immediately after installing Office 2011 or older since they will all conflict with the newer .ttf and .ttc versions.

Furthermore, I put Tahoma back because the "correct" .ttf font was displaying much thinner than the "wrong" old version in my critical app and I prefer the appearance.

The most likely reason it's displaying funny is because the font cache data is out of whack from having conflicting fonts active.

Remove the old fonts again. Make sure the .ttf versions of Tahoma are in the /Library/Fonts/ folder.

Close all running applications. From an administrator account, open the Terminal app and enter the following command (or copy/paste it from here):

sudo atsutil databases -remove

Enter your administrator password when prompted.

This removes all font cache files maintained by macOS and OS X. Both for the system and the active user account. After running the command, close Terminal and immediately restart your Mac.

Up to you which ones you want to use. Just as long as only one set of Tahoma is active. Since you prefer the older version, just keep the .ttf versions disabled. Also, delete one or the other of the old Tahoma fonts. They are literally identical. There's nothing to be gained by disabling one of them and saving the other.

As far as appearance, it is possible for them to be different. Both fonts are the same as far as how they're built. That is, all of the shapes are vector outlines. What would be different, due to large difference in their creation dates would be that MS has done a lot of tweaking to the hinting. And also possibly tweaking of the vector shapes themselves. There are other possible ways for the display to be affected.

Eventually, these old fonts and similar old models (like Type 1 Postscript) will be dead. All typography is being built around, and pushed towards Unicode. These old font structures have no Unicode support at all. They were designed and built before Unicode even existed. So I wouldn't be surprised that at some point in the near future, non-Unicode fonts will simply be disallowed and the OS will refuse to use them.

Generally, topics remain open even if the person who started it marks a post "Solved". Anyone can still add to it at a later date. It's pretty rare that the hosts will lock a topic. And that's normally because people are incessantly arguing minutiae points after the question has already been resolved. So, rather than deleting the topic, they want to leave it as it does have valuable information in it for others looking to answer the same question, but want to stop the arguments.