I think sadwidow raises a very important point.
It's very dangerous to set up a certain set of criteria by which to identify trolls. Because you inevitably risk labelling real cases false.
Some people say 'it's a gut feeling', well it can be, but it's difficult to get a genuine gut feeling from words on a screen rather than face to face. Some people say it's 'threads that read like soap operas', but many of my friends' lives have resembled soap operas at times, complete with twists and dramatic new instalments. Real dramas look exactly the same as fake ones. And a lot of things I've seen in real life I wouldn't believe if I read on here.
Some people label threads false because of confused or contradictory elements, but those are key features of crime victim testimony for example. Human consciousness and memory is fallible particularly where stressful events are concerned.
We must be very careful not to create a set of 'troll myths' that resemble rape myths. 'If I know that rapists look like xyz, then if I identify those factors and avoid them, I will be safe.' Trolls like rapists don't hide in dark alleys and look like ogres, you can't always identify them.
Imo, in order for this to function as an advice forum, we have to give everyone the benefit of the doubt, and if you don't believe a thread, don't reply. Disbelieving a genuine vulnerable poster here, is far more damaging than wasting time on a shyster.