Thunderbird 15.0.1 leaves behind folders AppData\Roaming\Mozilla\Extensions

Sometimes this gets left behind (it is not always removed by app), too - AppData\Roaming\Thunderbird\Crash Reports\InstallTime .*

And, it does not seem to clear this automatically when found, on restart.

On the other hand,
Firefox 15.0.1 creates and removes this folder, [AppData\Roaming\Mozilla\Extensions].

One thing I noticed is that Thunderbird creates a separate folder for
AppData\Roaming\Thunderbird\Crash Reports\InstallTime .*
Meanwhile,
Firefox uses AppData\Roaming\Mozilla\Firefox\Crash Reports
And,
AppData\Roaming\Mozilla\Extensions-BackupByFirefoxPortable

I thought that it might have been a conflict with having firefox running at the same time, but that is not the case.
As I have been using Maxthon recently, and I tried running and closing thunderbird when firefox not in use and the folder is left behind.