I think such an option would invoke more anarchy than order (well, headache for the moderators ). Currently we have "these" options for report, and it works like a bottleneck. Increase the number of options by 9001% and the number of reported threads increase just as much, with 87% more 'false alarms' than before.

If it's hazy, just report as spam and a moderator will check the thread out, taking the appropriate actions. The forums are as nice and tidy as always so the current options do suffice, no?

The moderators have stated that all reports will be checked, so basically it doesn't really matter what the reason is.

Nice idea

Yes from me.
But it would keed one new rule:
Dont spam/flame/etc via it.
10%warn for abusing it.