>>And I remember that at least fifty times (over the years) I had to update the message just because I used an I or B tag and then had a typo in the closing tag, which made the rest of the message (even across PRE tags), including signature, italic (or bold). So at least Firefox will keep it italic over many other tags.
>
>Yes, I will definitely enhance a few things in regards to that.

Worth bearing in mind that that the use of i (and b) tags is discouraged and should, where possible, be avoided:
https://www.w3.org/International/questions/qa-b-and-i-tags