LMA wrote...The show really guides my mental image of whatever I read. Because the show didn't really go there, I never really expect the characters to go too far into that area
Totally agree with you there! I've only written one story for L&C, but I've written quite a few in another fandom. When I'm writing, I try and keep a picture of the characters in my head, and write them accordingly.
Did we ever hear the characters swear on the show? I'm trying to remember but I really don't think we did. It would've been really out of character, especially for Clark, and I think that kind of carries over to fanfic.
Speaking personally, I work in an area that's very male-dominated and the average age of the staff is around 18 or 19. So I do tend to hear a lot of profanity. I limit what I say myself, especially now that I have a toddler that's learning to talk! The odd swear word doesn't really bother me. It's when it's over the top that it gets to me.