Ok, so I found it! It's in the frontend, in managing recording rules, there is the default recording template which can be edited (but only in the frontend, not via mythweb, which doesn't support this).
It's actually a "key new feature" according to http://www.mythtv.org/wiki/Release_Notes_-_0.26
but I really haven't noticed before, using mythweb most of the time for scheduling recordings.
Anyway, +Brad Stone
, thanks for the help and pointing me in the right direction, even if it was in a round-about way. :)