Sorry you're having to deal with that, I totally get it's annoying.
Not saying it definitely isn't deliberate, but I wouldn't necessarily jump to this being malicious. There are still plenty bots out there that will crawl webpages and pick up email addresses to add to spam lists. They'll undoubtedly crawl places like this, so if you're putting your email in plain format in your posts, that's fairly likely to happen. Plus obviously anywhere you're signed up to can leak your email any time.
I've had previous email addresses get the kind of spam you describe, and it only takes a single instance of it being leaked or in the wrong database to get spam like that in the hundreds of emails per day.
