i don't know if there is a module that does what you want, but it is relatively easy to check. i've read that even just checking the letter-pair distributions will give good indication whether a group of texts are written by the same person.

I am not a troll.

'I<space>' => 1
'<space>a' => 2
'am' => 1
'm<space>' => 1
'<space>n' => 1
'no' => 1
...
[download]

count the letter-pair distribution for a bunch of Stinker and Slinker's posts, and a bunch of other users posts. if you're lucky it will be obvious if they are truly the same person.

let us know what you find out...;)