by Standard8 (Developer) on Jan. 20, 2021 · permalink

Conversations shows you a setup screen where you agreed for it to make changes - it makes some by default, but you can review the changes as well. The description also gives hints as to what to do to revert things you might not like.

As also stated in the description, quick reply is not currently working, but is being re-developed. Unfortunately changes in Thunderbird required extensive rework that has not been quick and easy to do alongside the other changes that are required to keep the rest of the add-on working.