If you flag a post from that user for moderator attention, it is highly likely that we will look at their other recent activities, including (but not limited to) questions, answers, comments, votes - and correlations to other users if there is a suspicion of a sock-puppet.
If they are being a nuisance, there are a range of options - but also don't forget that just because they've annoyed you doesn't guarantee that we're going to throw the book at them.
The e-mail approach works too, but don't forget the team is US-based, but between us the moderators have pretty-much the whole day covered; if they are actively an issue, a moderator flag may get acted on quicker than the e-mail. Or do both.
Also; don't forget you can vote... if somebody is being offensive, vote them as offensive. For most puppet accounts, the penalty (100 points) may be enough to take away much of their access.