Sorry - I thought it was clear from my first comment above: I am able to reproduce the two problems reported by GiraffeSilver above, using (among other sites) try.discourse.org.
My screenshots would be identical to his.
EDIT: Posting 2 examples, for completeness (thought to save space…):
EXAMPLE ONE: Browser Copy/Define/Share above Discourse’s Quote Reply:
EXAMPLE TWO: Comment becomes full screen
