Assegnate 2 su 5 stelle
Does not work on Thunderbird 31.1.2. The export process was successful (as far as I can tell), but the import failed (no rules were imported) although it said that it was successful.
That being said, as other commentators have mentioned, the filters rules for any account are simply stored in a file called msgFilterRules.dat, that you can easily find in your TB profile folder. You can just copy that file into your new profile (and maybe you have to restart Thunderbird) and that's it, no extension needed.