When sending emails from a phone, typos happen and brevity becomes a way of avoiding stress. From Thunderbird, I use these two limitations to give a dash of friendliness to my short emails, and add a line that say something like "This email was sent from a mobile device, sorry for brevity and tpyoes", with that final typo made on purpose.

But I can't do this because the signature is shared between desktop app and mobile phone.

I understand that this feature would take 2 months of programming, but hey, if enough people have the same idea maybe we can make it happen.

Or maybe someone has found a workaround (no additional apps tho)?