Threaded message list collapsed even with mails marked as important

Hi,

in the threaded message list, threads will collapse if all mails are 
read. This is a bad idea if there are mails marked as important. 
Important mails get lost this way.

If there are important mails in a thread the thread should get expanded 
by default. Like if there are unread mails.

(Is this some kind of a feature request or even a bug? What do you 
think?)

Is there some option to change this behaviour? I'm using Roundcube 1.5.3 
with Kolab 16.

regards
hede