Anecdotally, I'm getting a lot of obvious spam on my repos that are >4 years old and less spam on other repos. Also, my "org account" (from before orgs were a thing / fully featured) got more spam than my personal account (which I don't use often these days but does at least book a commit or two most months).
So, the spammers are probably intentionally targeting repos where folks aren't likely to bother marking as spam.
On a separate note, I do not understand why people care so much about mid-quality t-shirts...
> I do not understand why people care so much about mid-quality t-shirts...
Most likely a mix of "it's free", "it's easy", and "it looks nice on a CV". Perfect storm for a lot of students and juniors to spend an hour of their time on, without bothering to spend the extra two to actually make the contributions useful.
So, the spammers are probably intentionally targeting repos where folks aren't likely to bother marking as spam.
On a separate note, I do not understand why people care so much about mid-quality t-shirts...