[puenktchen]

It seems MediaPortal doesn't use any of the standard Kodi language IDs but has its own.
In theory following should be okay, but somehow $ADDON[] doesn't work when used in a string comparison:
Active Timer ->

Code:

<visible>StringCompare(ListItem.Comment,$LOCALIZE[305])</visible>

Active Timer Rule ->

Code:

<visible>StringCompare(ListItem.Comment,$LOCALIZE[305]) + !StringCompare(ListItem.Timertype,$ADDON[pvr.mediaportal.tvserver 30110])</visible>

Hmmm, just what I thought. The PVR addons are not maintaining the same standards.
Anyway based on your info I've done some modifications again. I can't test it myself so please test in the next skin update (later today or tomorrow).

If your change is in version 3.6.80, then it's still not working unfortunately.