When moving filters in the filter list with the keyboard (Alt+U and Alt+D), the filters are automatically disabled. This does not occur when using the buttons (Move Up/Move Down). Using TB version 1.0 (20041206).
Reproduced with TB 1.0+0222, Win2K. Also seen in Moz 1.8b-0120.
Linux too, Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1a2) Gecko/20060519 Thunderbird/2.0a1 ID:2006051904.
This is still an issue in FF2. Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:22.214.171.124) Gecko/20070309 Firefox/126.96.36.199
very possible dupe to bug 368218 (more active there..)