100% all of the above.It's difficult for me to group people into "likeable" and "not likeable". People just are and I observe them.
One policy I follow is that first, second, third, whatever impression can be false, there are always some underlying reasons to people's behaviour, so I try not to underestimate people and always give them a chance. People have better days, worse days, they change, so they might give off positive or negative vibes, depending on them and myself. Therefore, in a way, I "like" everybody because I want to see what will happen.
It's situational for me, something they say initially catches my eye, whether it's something funny, smart, insightful, fitting my mindset at that particular moment. I don't look at type at all. When a particular person catches my eye, I tend to "focus" on them for a while to get some kind of a picture of them, whenever they post in the threads, they just pop up more than others. When I have done that, I move on to somebody else and the previous ones are saved in the "bank". So, when I happen to encounter them again in threads, I immediately get the sense: "Oh, he/she gave me a positive/negative vibe the last time, what will it be this time?". It's like mapping people I observe.