If a persons profile now shows their Comments being 0, they most likely got banned, eh?

Well, typically the sign of someone being banned is when their account says Level: Banned.

okay, so then what would account for their comments being scrubbed? Would that be like a suspension?

There's the trust level. If had made a bunch of comment that broke the rules, say for example spamming that your DM's are open, all that would be purged. The purged would mean the trust level is now so low they lost access to mail 'til built the score back up.

ahhhh, okay, thanks

Just out of curiosity, what are the levels (mine currently says "member")?

Pretty much just what your status is. I regular user, part of the moderation team, banned, etc.