How likely is it for a student to be expelled from university for online posts they wrote as a minor? There have been stories recently of students who were expelled from university for derogatory things they said online. It got me wondering if a student would be expelled for saying something derogatory online, except when they were a minor. In this scenario the student wouldn't have been 17 (right before they entered college) but more around the age of 13-15 when they made the comments (many years before enrolling).

I know this probably depends on each university's own code of conduct, but I have no specific institution in mind. Answers based off your own university are fine, and I'm more interested in Canadian universities (although members of universities in the US, Europe, etc are also welcomed to share any info).

To me it doesn't make much sense for a student to be punished for something they said years ago as a young teenager, but I digress.
I'd say it's unlikely for a student to be expelled from university for on-line posts they made years prior. It may impact the student's reputation and may sway acceptance decisions in case of multiple potential candidates for a course or curriculum with limited capacity for students, but being expelled for such a thing would actually not reflect well on the university in question and may actually have repercussions for the institution.

Of course, it strongly depends on many factors; the nature of the posts, the association with certain groups or not, individual student acceptance rules and conduct rules of the university and what is considered "enough time passed" to reduce the weight of those posts.