I do attribute reading PUA stuff for my creepiness.

One of my friends, who actually studied so much PUA that he briefly became a coach, was very good at not being creepy. The way he did this was being clear about his intentions. Not necessarily explicit: he would still use innuendo etc. The point was, if he was into a woman, he would flirt with her a lot, assuming she was at all warm to the prospect. If not, he was still very friendly, but interacted in a markedly different way.

This meant that women don't have to guess about what he's up to. He recounted a story that took place in our university residence, involving another male friend of ours and a female friend they both knew. We'll call my PUA friend K, the woman F, and the other friend B. So, F was sitting in her room when K pushed her door ajar, saw her, and then went it and sat down on her bed, and said something to the effect of "Hey, what's up?"

F responded warmly, "Oh, man, the weirdest thing just happened... B just came into my room unannounced and started talking to me... it was kinda creepy..."

K paused, and asked with a grin, "You mean, just like I did, just now" and she reflected that yeah, the behaviour had been almost identical. The key difference, they agreed, was that K was always very open when he was into someone, so his platonic entrance was seen as being that: platonic. B, on the other hand, falls into more of the Nice Guy category.

Bayes' Time!
For K, if he's into a woman, he almost always flirts with her. If he's not, he does a little, but sparingly. B, on the other hand, rarely flirts (proficiently) with women. In fact, he might flirt more with women he's not into, because he has less fear of rejection. But to within error bars, he basically doesn't flirt.

This means that K is providing very strong evidence to women about whether or not he's interested. As mentioned, he backs off when they appear not to be as well, which is irrelevant to the comments about evidence but important for clarifying that he's not obsessive. B does not. B doesn't really give any evidence at all, and the resulting uncertainty is creepy/awkward/uncomfortable. It makes women uneasy, because they aren't sure of his intentions. If they knew he liked them, they might be able to update him on whether or not they do. If they knew he didn't, then they could relax. But not knowing sucks.