I report trade channel spam ALL the time - it saves me an ignore slot. I don't contribute to the spam by saying "reported" in-channel though.

I report offensive names ALL the time. I don't engage with them though - not even to gloat about how clever (sic) I am that I reported them - it's for the GMs to sort.

I also run SpamMeNot (hooray!) to block gold sellers in ALL channels, and that auto-reports.

In short, if you could get into any trouble by reporting too much I would probably know all about it by now