The post is worded like they were in college at the time. College students can register to vote in either their home state or the state they attend school in, just not both.
There is nothing on their post that implies age or student status, unless you think staying with your parents is something that only college students do and is not possible after graduation.
There also isn't anything in their post to say that they're not. But you're assuming it was illegal, based on... what? Why assume the worst rather than the more charitable assumption?
and you're assuming it was legal, based on... what? Why assume the best rather than the more realistic assumption?
Right, so you’re taking the least generous interpretation of the OPs statements and concluding they broke the law.
Please don’t that, it’s bad faith and needlessly divisive.