So far I've been sorting my emails in non-threaded view, by star, then by date. Understand, first all starred message (sorted by date) then non-starred message (also sorted by date)
Either this doesn't work in TB 38.6.0 or there is clearly a bug, but the above gets wrecked in a weird way when using threaded view :
Suppose I have initially the aforementionned non-threaded view sorted by star then date. Now I click the thread button. Messages gets threaded in the right way: pseudo-starred threads first (ie. if the thread contains at least one message that is starred it still appears as a threaded message even though the "façade" email is not starred) and then non-starred threads also by date.
Now I switch to a random view, and then I switch back to the view I had just "threaded". That view is now completely destroyed. The messages are only sorted by star (and, only if the façade message of the thread is starred), the date sorting went to the trash, I have emails from 2009 next to 2016 =_=.
Seems like a bug, but I couldn't find it on the bugtracker ?