I can see likes/comments on my shared photo stream on my iPhone but not on my MAC in Photos - why not?
iMac (21.5-inch Mid 2011), OS X Yosemite (10.10.3)
Are you talking about iCloud Photo Sharing? If so, make sure it is turned on on your Mac.
Yes. On my phone I can comment and like the photos. On my MAC when I view the shared photostream I can't see likes and there is no option to like the photos or comment on them.
To avoid confusion, if you are talking about iCloud Photo Sharing, please don't refer to it as "the shared photostream." There is another iCloud-related service available in Photos Preferences > iCloud called "My Photo Stream" so when you combine parts of the names of both of them, it is difficult to know which service you mean. Using the "official" name of the service also will make it easier for you to find relevant help topics about the correct one in the builtin Help for Photos or in the online version. Also, iCloud Photo Sharing allows you to have many different shared albums, each with its own name, so using "the" can be confusing.
Anyway, all the shared albums are grouped together under the "Shared" section of the Sidebar or toolbar, along with "Activity," an overview of the activity on all the shared albums, arranged by date. The "Activity" view shows each photo, which shared album it is a part of, & the comments that have been added to it. In this view you will see "Like" in blue for items others have added to the album (but not for ones you have added) & clicking on that will add your "like" to those photos.
For comments & to add a "like" to items you posted to the album, refer to the Comment on or like a photo in a shared album section of the Subscribe to albums shared by others help topic. (Don't ask me why it is in that section -- Apple sometimes has some strange ideas about how to organize help topics!) This is what it says:
It can be very difficult to see the + mentioned in step 2 -- it is a thin white plus sign in a white cartoon bubble outline (& the plus sign will change to a number when the item has been liked), but it is there & the pointer will change to a pointing hand when you are over it, which helps a little.
Thanks. Sorry for not using the right terms. So if I am viewing a shared album then I can't tell which photos were liked unless I double click on each one and see if in the message box it has been "liked" - right? I am trying to work with someone on a shared album and looking for a way to see all the thumbnails with little hearts indicated (like is does for the non shared albums I have in Photos) vs. having to double click each one to find out. Thanks for your help.
There is an option in the menu that pops up when you click on the 
button that appears in the toolbar when viewing a shared album that enables notifications when subscribers like, comment, or add photos to it. Alternately, you can use the "Activity" view to see that info.
like or comment on photostreams on my mac
