Defamation: Posting Someones Pictures Online Without Their Permission

My question involves defamation in the state of: I was a part of a little online forum in which people would occasionally post pictures of women that they had encounters with. It was never nudity and it never revealed the identity of them.

I made a thread before and had posted a picture of some conversations I had on tinder with some women. I'd show their profile pictures but would edit the photo so it couldn't be reversed image back and could they would never be able to find these girls. Is this defamation? I've gotten out of control on this forum and I post and participate on there just because it's entertaining and funny. There a jokes that people put on there that a lot would find offensive. One thing that really got me thinking is I posted a comment which is a frequent joke on this forum "If she is 17 than I'm 17 know what I'm saying" I'm not a creep in anyway and I am not much older than 18 myself. I had a female user say that I could get in trouble for defamation and she said she's going to report me for my comment.

I'm getting off of this forum just because I'd hate for any of this to touch my personal life. It's all just vulgar humour. I also live in the state of CA.

Defamation: Posting Someones Pictures Online Without Their Permission