This is the internet, and the internet, by its very nature, provides a platform for people to pretend to be something they're not.
In that way, it's healthy sometimes to trust your instincts as guidance for yourself. This doesn't mean you have to believe your initial instinct to be the absolute truth of the matter - because it's very easy to misjudge on the internet and to misjudge because of our own history. So, accept what you feel, but try to handle it as a possibility, rather than a reality.
If you feel emotionally ok to do so, ask the person questions to clarify things that you are unsure about. If not, step away and allow yourself not to get involved. Whilst there is a down side to the anonymity that the internet provides (people pretending), there is also an up side, and that is, that they can't get to you, and you can walk away from people much easier than you can if they were there physically. In that way, even if they were an abuser, you are safe as long as you don't give out your personal address etc.