The display layer for inline comments hasn't been updated in a long time is currently under-engineered.
We have a large number of glitchy interactions because the various components are too loosely organized. For example, the keyboard selection reticle and inline edit workflow basically break every time they interact between them because they aren't really aware of one another.
I plan to rework the display layer to generally follow the patterns present in the Workboards code. (Conpherence will also get an update in this vein in T12562.)
[ ] Restore "h" to collapse or expand files.
[ ] Determine if we need to cache cursor state DOM information for keyboard navigation ("n", "p", etc) for performance.
[ ] Fetching comments by ID doesn't find comments which haven't been interacted with yet.
[x] Restore "r" to reply to inlines.
[x] Restore "e" to edit inlines.
[x] Toggle file action doesn't yet interact appropriately with inlines: you can still "j" and "k" yourself over hidden blocks.
[x] After a keyboard-based "reply" or "edit" operation completes, we don't put the keyboard state back where it was, exactly. We're close on "reply" but less close on "edit". We're also far off on "hide", where we lose comment state.
[x] The ability to undo a discarded edit has been lost.