[Pyramus]

I'm not saying the content of a post can not be personal data. I'm saying it is not by default.

The words "Hello world" posted on any subreddit is not personal data. In this case the company could simply delete the information relating to you such as user name, IP etc.

The content you post is not, in general, personal data. It certainly can be.

[Tao3300]

That's kind of funny, because "Hello World" gives a strong indication of your profession and interests. Not enough on its own to be PII, but a useful data point.