In other words, why do you believe that PrawnOfFate is a troll, and not someone who is genuinely confused ?

"Troll" is a somewhat fuzzy label. Sometimes when I am wanting to be precise or polite and avoid any hint of Fundamental Attribution Error I will replace it with the rather clumsy or verbose "person who is exhibiting a pattern of behaviour which should not be fed". The difference between "Person who gets satisfaction from causing disruption" and "Person who is genuinely confused and is displaying an obnoxiously disruptive social attitude" is largely irrelevant (particularly when one has their Hansonian hat on).

If there was a word in popular use that meant "person likely to be disruptive and who should not be fed" that didn't make any assumptions or implications of the intent of the accused then that word would be preferable.