I can’t believe I’ve never noticed that “Show More” button before! That’s handy! I’ve always just opened the observations in a new tab if I wanted to see the rest of the info.
However, having now used that very handy button, I see that the button text always says “Show More” even when its function has changed to “Show Less”.
I think this might be more of a design choice than a bug per se. That is, “show more” is “activated” when you click it and then “deactivated” when you click it again.
If it makes you feel better, I went 4 years without knowing it existed and I thought I knew every trick to the site, so much so that I was in disbelief and doubted the person that told me that it wasn’t a new feature
Oh I see now (I don’t speak German so didn’t notice that in your screenshot).
It looks like it does display “show less” when expanding lists of followed users’ recently uploaded observations, but not when viewing additional IDs/comments on an observation, flag, or elsewhere.