May sound like a trivial thing, but for readers and authors its actually a little bit of a nuisance (at least, to me).
Basically, if you look at the roleplaying boards, the signatures are disabled there because they distract readers.. I think the same applies to fan fictions as well, especially if it is chapter formatted. I mean, if you haven't written one before you have to realise that one shots usually take an hour to write at minimum and then there is editing and formatting... the readers should not have to see signatures, especially all of the GIFS you crazy kids have in yours these days.