[martin_a]

It wasn't opt-in the last two years, where repos where flooded like nothing and the organizers didn't seem to care much and you as the repo owner had to flag spammy stuff.

That leaves a bad taste.

[MattIPv4]

Opt-in was added in the first few days of 2020 after the massive spam wave. It has been opt-in ever since that point.

https://github.com/Hacktoberfest/hacktoberfest-2020/pull/596