All I can offer by way of remedy isn't a solution to your specific problem, but maybe something that you can live with.
iTunes > Window > Mini Player
Grab the top edge of the album artwork this displays and shrink it down into the control bar until you can't make it be any shorter. Then do the same with the width. You will find that there are very few places to grab and drag this at this point, but just between the Close box and pop up Volume Adjust icon is a good place to yank it around into the top right corner of your Desktop where your Notifications appear. You normally look there to see what the next track is and sometimes aren't quick enough to glance over at the Notification before it is swept away, so now the Mini Player just does the same job, is there permanently, and actually takes up less screen real estate. Notifications will slide over this Mini Player even though it floats above all your open Applications for ready access. Soon enough muscle memory will let you slam the mouse cursor into the top right corner and then back a couple of inches to hit Play / Pause / Next
Unfortunately, this is the best solution that I can come up with until people make enough complaints to Apple and they update High Sierra to revert it back to the more ergonomic way it used to work. I don't know if it is something they can fix, or if it is down to Google, but I would like to see the icons that overlay YouTube videos be more widely spaced so their active areas can be expanded for touchscreen operation on my iPad Pro, also as I keep having to clean its screen of greasy finger prints from watching videos whilst cooking in my kitchen I'd like to be able to use my attached hybrid keyboard cover to Play / Pause / Next / Reload with Space / Space / Cursor Right / Cursor Left so I can keep the screen pristine, this doesn't interfere with comments as it won't think that you are editing anything until you tap on the input field to give it keyboard focus, although I suppose you could have Command E replace that finger contact, then Command P again to post your comment, using Command D to discard your comment.
Well, I'll shut up now as I'm just rambling.
:-D