WRQS959

Tones are not required; but unless you want to completely make a channel useless to any other repeaters on the same pair and potentially cause all kinds of interference you really should have one.  If you're running a machine CSQ it'll pick up ALL traffic and any background noise above your squelch level on the repeater input channel, regardless of if it's intended for your repeater or not.

FCC rules do not require tones. The reality does.

Tones are NOT required on any channel or device. Ask whoever gave you that tidbit to show where it is required in the rules.

Whoever told you that is either an idiot, a liar, or quite possibly, both.

The trouble with a Carrier Squelch repeater is that it will repeat literally everything it hears. There's no real control, and if you're high up, you'll hear the world, including stuff that you really don't want to repeat. If you've got any other co-channel user close by, your repeater will be keyed every time one of their mobiles is transmitting. Not ideal, not even close to useful, and pretty much guaranteed to be a pain to your neighboring system.
I don't see anything in the rules that says you have to run PL, but the FCC does say you're supposed to avoid interference and monitor before transmitting.