There's a bug in the Android app where a comment can be typed in but not posted, meaning the post button does nothing and I have to back out of the question and go back in to post the comment. This definitely happens when the screen rotates, and also other times but I haven't identified them exactly.
I have version 1.0.78.
Edit: This had stopped happening but now started happening again when I updated to Android 6.0.1, now with version 1.0.85.