It's quite annoying, whenever I return to a card, the last comment is written in the text are as if were a draft, even if it was already sent. Everytime I go comment I have to delete the previous one from the input.
This is not expected once a comment has been submitted. The symptom suggests that Trello may be retaining stale local draft data, so I would isolate that first:
Open the same card in a private or incognito window. If the old comment is no longer present, disable browser extensions and clear the cache or site data for trello.com.
Try the same card in another updated browser. If it only happens in one browser, the problem is local to that browser.
If you use the desktop app, select Help → Reset local data, close the app completely, and reopen it.
If the sent comment returns to the editor in incognito and in another browser or device, record the browser or app version and a short screen recording. That would suggest a Trello regression rather than a local cache issue.
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