True. What annoys me the most in apps in general (Jerboa included) is the practice of losing your draft at the minor deviation of usual workflow. You gave the example of hitting the top bar, but the same happens when there's a connection issue or if the app crashes or is closed by the OS to manage memory.

The comment UI is being reworked to match the current post UI in the next set of nightlys

Use the fab reply function

Create a comment view has been reworked and is in the codebase though there are still improvements to be made.

With the new create comment view, the create button is on the top bar so it's always accessible. Touching the top bar will not close the create comment dialogue either.

There is still the issue of a comment draft not persisting and your place in thread being lost after creating a comment. The latter being a particularly annoying user experience for myself. I'm hoping one of us will be able to address that soon. A few of us haven't had a lot of time to work on Thunder lately, myself included :(