Mostly quite obvious stuff, but might be of interest! The gist of it seems to be that trolls want to annoy you for their own amusement (as one of the commenters on the guardian article points out, this is not the same as people paid (by oil companies, etc) to disrupt serious debate), so perhaps the worst thing to do is get angry and write abusive comments back to them, although the study seems to favour ridiculing them openly...
The abstract of the paper from the Journal of Politeness Research (!) is here:
 http://www.reference-global.com/doi/abs/10.1515/JPLR.2010.011
Summary from the guardian here:
 http://www.guardian.co.uk/education/2011/jun/13/internet-trolls-improbable-research