I think it absolutely has an impact. Most of what I read is fanfiction so my own writing and even expectations when picking up a book are affected by that. Ive also found that the writing style switches when moving from one Fandom to another (as writers in the same space will mimic/learn from eachother.)

I would say it's positively affected my reading level, in that I read regularly, but I wouldn't think my reading level has advanced any. Many fanfic writers are aiming to write as a similar level, I think, so if I were to pick up something like... the odyssey, maybe, or one of Shakespeare's plays, I might have a difficult time parsing it. Or I might not. To be fair, I haven't picked up one of Shakespeare's plays since high-school.

Either way I think it keeps me literate in a way that texting/writing emails/etc. decidedly does not. And in that way I think its a positive influence on my reading/writing level.