Rated 4 out of 5 stars
twaddle at https://addons.thunderbird.net/en-US/thunderbird/addon/refwdformatter/reviews/170039/ is not missing anything. Only 1 level of quoting is being removed, the deeper quotes will remain in place in the mailbody. try fix this yourself at: https://liveweave.com/OerYQu and make a pull request on github if successful.
The ReFormatter ThuBi-extension works for usenet news as well as regular e-mail, but it only cleanses the mailbody not the header. 4 stars only since the real problem is not being addressed, which is not the mailbody but those darn "Re: " prefixes in the subject lines, i.e. the mailheader.
4 stars only also because it should be made quick and easy to understand what this thing is good for without spending 4 hours on it. Just use plain concise English to perform this trick, which only 0.1% of all programmers can perform. Well, maybe some just don't care at all for some reason.