Vent and chat give you a mask of anonymity. There are no lasting repercussions to what you say and do. That woman who sounds hot lives hundreds of miles away. You are safe to be your honest self. Free to say whatever without fear or real rejection (you can always transfer servers, right?). Playing the gentleman is for rl.
As a woman, there is also a feeling of security in WoW that does not exist in rl. No expectations or obligations, just the potential to have a really great time. That faceless voice could belong to anyone, and the potential for fantasy is thick. Unfortunately men (boys) blow it by being idiots.
Women want the seduction, the romance. They want to feel beautiful and alive; they don't want to hear about chili dogs or rusty trombones (look them up, I'm not even going to link them for you). It's just not sexy. If you are a male interested in online flirtation, the best thing you can do is make a woman feel desirable. Subtlety is in order. Suggestions of soft caresses, simple things like wishing you could feel the texture of her hair, can make her breath catch. What would her skin feel like if you were to brush your lips along her neck? Would your hand feel hot against her back? Little things. Let her imagine. And, just for the record, asking a woman (out of nowhere) what makes her pussy wet is NOT seductive. RL is full of assholes, don't be one online (in this regard -- in a raid, fine).
Who knows? Being a bit more gentlemanly online may help you develop more finesse in rl.