I use the app quite a lot and have never noticed the bug, a minor bug that could be remedied in the next update. I think there's a thread around here for reporting such bugs but I don't have time to find it right now. It's pretty simple to just tap "edit" and then tap "cancel" on the upper left. How often do you think you want to edit a post and then change your mind?
I was about to agree with you but after numerous tries on my iPod I'm finding that the center and bottom area of the cancel button could use some fixing but that the top half of the cancel button is 100% responsive.
I also noticed that I sometimes miss the 'modify' option about 20% of the time.
Personally the thing that's most annyoying to me is the size of the 'open advanced options' and that I always have to tap the 'close advanced options' multiple times to finally get it to work.
Lastly, I guess in this case, it's fortunate that this thread exists on it's own versus amalgamation of TH55's observations