What Herbert says about Gil is that he has quite the reputation and is someone to stay away from, doesn't imply Edgar specifically. This could easily be referring to the rumors about Gil being inappropriate with his students rather than anything to do with Edgar. we know Walter was an adult when Gil started touching him, but Gil may have been falsely accused of touching a minor, and maybe Herbert believes it
Lars is there when Gil says he's a virgin and his response is "....wow". If they had slept together I think he would've reacted differently.
Most of the server seems to think Gil meant that the same bad decision would be getting back with Lars but I'm not sure. Gil does say he asked for Parker to stop him, and that Parker means well.