And no, it's not a pluralization "bug".
Consider the UI enclosed in the red hand-drawn circle:
The above image was captured from http://chat.stackoverflow.com/rooms/info/10/loungec/?tab=stars
When I clicked on the orange "by me" link I was expecting to get all the posts I've written that have at least one star. Instead, I get a list of all posts that I've starred.
I read the above as "Starred posts by me", which to me meant "Posts that I've written that have at least one star". "Posts by me" can imply authorship the same way "books by me" or "books by Herb Sutter" implies authorship. I didn't think it meant "Posts that were starred by me" when I read it. Hence, the ambiguity.
With that interpretation, the "by everyone" link is also inaccurate, since there isn't a single post on Chat that everyone has starred.
As a result, the labeling is somewhat unintuitive and doesn't best reflect what each one does. At best, it is ambiguous.
Because of the English language's terrible syntax, I propose that the UI should say something like:
All starred posts | Posts that I've starred
to better reflect what I actually get, or instead implement functionality that would allow me to see all posts I've written that has been starred by other people.