It's very difficult to both A) have meaningful conversations in a public space, and B) conceal your identity from a dedicated adversary. Once a person has a long post history, it's likely that an observer could narrow down their identity to a very small group, if not a single person. Every post you make reveals something.

Even if you don't ever explicitly state it, your age range and gender can likely be guessed with high probability by your writing style and/or little tidbits of info you leak without thinking about it. Same for political leanings. You might casually mention the brand of car you drive, or your favorite foods, or just reference something you experienced as a child that is not universal. All of these things leak information, and while each one seems insignificant, in aggregate they can tell a detailed story. Just knowing that you're a Canadian who speaks both French and English eliminates about 99.8% of the world's population as possibilities.

Back on Reddit I used to create fresh accounts all the time, but then I'd go and join the same subs, post with the same writing style, and generally express the same worldview. If anybody cared, had a good grasp of statistics, bothered to collect the data, and put in a stupid amount of time to it, they could likely match all of my accounts together. I was never too worried about this because....well I just didn't care. But I did have a cyberstalker at one point and it made me think.

I wouldn't be shocked if someone could match me to one or more of my Reddit accounts just from this one comment, tbh. I'm leaking information here like a sieve! Not many people have the skills to do that, and the few who do are unlikely to give a rat's ass about me. HOWEVER, as AI becomes more advanced, anyone with computer literacy will be able to do analysis in minutes that might currently take an expert days or weeks.