I also was refering to Doc not talking face to face. I doubt 85 Doc would have passed out because he is aware of time travel , and the fact that he would be talking to his past self before he even turns around (again) , perhaps you mean 55.
I agree that the Jennifer situation still could have been bad, even though it could have made 'one' think that talking face to face is ok afterall.
I'm on the side that Doc's opinion was not changed by knowing this anyway, and he still refused to try to 'Talk To Himself' because there could still be risks.

The original Poster was talking about face to face! Sure, the Jennifer sitch didn't blow up the universe but she passed out! If doc isn't there to scoop her up and out of the house then what!?
What if 85 Doc passes out and now he's out of commission pretty scary cause he's an essential part to furthering the plan at that moment!

Who knows how the conversation could have gone. Despite claiming to never want to know anything about his future, he eventually figures what the hell and reads the letter, so who knows what seeing and interacting with his actual future self might have done to him. He may have been overwhelmed with the what the hell attitude and starting asking a bunch of questions. If the conversation went on too long other things could be altered in a way that prevented previous events from occurring. 85 Doc knew even though the Jennifers situation didn't blow up the universe, it also had little impact on changing future events.

He knew that Jennifer saw her older self without any consequences..
The faint was still a major inconvenience that could have led to a lot worse things had he not been there to carry her away.
So in a way, that was still a big consequence / risk. Way too risky.
You'll kill everyone!
But Ice Cream Cake!

You would think that, with his intellect, he would have been able to handle speaking to his past self. But he insisted not to do it, so he practiced what he preached.