(In reply to newsfan from comment #13)
You could experiment with that in FF to see whether you can create the "br" (Body Text) behaviour.
Thanks for the information, that is very helpful. We have a test website here: https://rugk.github.io/unicodify/ with the three standard browser input types. I was able to modify that locally to also support these two Thunderbird modes.
However, I am still not able to reproduce this regression in Firefox. In TB 102 with this "Body text" mode enabled, hitting enter adds two line break elements, but in FF 102 with the
br separator, I just get the single line break element as expected. For reference, here is the code in our two add-ons that triggers this regression.
Nothing in the regression range points to changes in the compose window editor. What's the corresponding M-C range?
I am not aware of how to get the mozilla-central range from mozregression (when testing TB), but from manually looking up the pushes in that time frame, here is the range: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=d75eb3fb217f93514703f74785fa7b08281fb279&tochange=e1d1107d438bbdad13a5c4f62911295ac8a16fcf. There are over 150 pushes, but bug 1766355 looks to be the most likely culprit.