This is the sort of thing that you presumably get trained out of pretty fast, but it's kind of annoying the first few times it happens.
If you start writing something in the "What is on your mind" edit box on the left, and then notice someone says something you want to respond to, and you hit the little 'Reply' arrow under their toot, your existing text is discarded with no undoo possible (as far as I can tell.)
This is the sort of thing that you presumably get trained out of pretty fast, but it's kind of annoying the first few times it happens.
If you start writing something in the "What is on your mind" edit box on the left, and then notice someone says something you want to respond to, and you hit the little 'Reply' arrow under their toot, your existing text is discarded with no undoo possible (as far as I can tell.)