I don't see sending a quick message as negative in any way, I actually find it positive.
To me I see it as a form of networking.
Now, if someone wrote saying that someone told them to contact them. Or if someone wrote a message once a week when the other person didn't reply.. Or if there was harassment involved, that is a different story...
But a simple, "hi! I saw that you would see kimmy when she was around.. I have seen a few gents who say that I remind them of her. If you're ever in the mood to make a new friend, feel free to get in touch.. Xx" - I have never done that, but I find it totally acceptable.