Even if it’s from the GPLv2 OpenJDK?
For a comment that has been “liked” by one or more users, it’s now more difficult for the signed-in user to see if he or she has “liked” that comment.
Previously, comments liked by the signed-in user were indicated with a red heart, while comments liked by others, but not the signed-in user, were not colored. Now the only way for the signed-in user to know which comments he/she has liked is to click on the count/number to see the list of users who liked the comment, as the likes are all the same color now.
That’s a less-than-useful homogenization.
I don’t think so.
What they have done is split the function that used to be a single function on the right hand side below the post into two functions, one at the left and one at the right.
Yes, you can see whether you have liked a post by clicking the left heart and looking for yourself but that is less convenient and also, if there were a large number of likes, not very practical.
But the right heart does change colour to indicate whether or not I have liked (grey outline of white-ish heart if not already liked; light-red solid heart if liked). And also you can just hover over the right heart to see your status (tooltip of “Remove this like” / “You can no longer remove your reaction” if already liked - in addition to another visible difference).
I assume we are both still / actually using Firefox 157? Maybe you have over-customised / over-themed? 
Edit: PS And of course the left heart might not actually be a heart, as a result of this change. Might be some other icon. Might be a combination of icons. And the right heart might not actually be a heart either.
Ah… true! I hadn’t noticed that yet.
Yep. And Nope.
Sorry… Not familiar with such a concept. 