Hmm. I agree re. utility of drawing newcomers' attention to it. I'm still not sure opt-in is the best way to do that, when there are other measures that achieve this and bring other benefits (such as an improved "newcomer experience" - i.e. some kind of tutorial or page with suggestions) without any opt-out problems.

Put another way, if the goal is to draw newcomers' attention to something, then actually drawing their attention to it seems to me a better approach.

FWIW I don't feel strongly about participating in meet-ups either, but opt-out seems to be done wrong by so many organisations that I set the bar pretty high for what I'll agree is a reasonable justification. When all the purported benefits of an opt-out arrangement don't actually depend on it being opt-out, I am sceptical. :)