Encountered on iPhone/safari, so may be just an iPhone thing, but…
When I delete all the content from the composer it freezes up and won’t allow me to discard or dismiss. A refresh is needed to regain functionality (and brings back the previously deleted content).
Basic step-by-step:
Open the ‘reply’ composer
Type some stuff
Select everything and delete or cut
Then the composer becomes unresponsive and needs a refresh to work again.
After a few attempted repros, I seem to get a better repro rate when using a quote rather than typed text (though typed text can still trigger it intermittently).
Highlight a portion of text in someone’s post, click ‘quote’
Reply composer opens
Select composer contents and delete/cut
Composer is unable to be dismissed or reply discarded