Suggestion
While threat "rooms" with a single type of monster are fine, tension rooms are never created in cavernous levels, which is intentional behavior (http://www.adom.de/adom/report.php3?ident=2134). I suggest this is reversed so that both kinds are allowed in these levels, even if they lack rooms in the traditional sense.

Why it'd improve the game
Most cavern areas are of high danger level, which means random tension rooms can have some pretty powerful monsters generated within. This is challenging, and adds to the fun of the game.

Notes
This is a follow-up of issue #1815, which I mistakenly filed as a bug report.