I think your modesty is unwarranted. :-)

Meetups have the potential to lead to a lot of updating, positive feedback loops, and other real benefits for the attendees. I suspect that very few comments on this site, even the higher rated ones, can match them in that regard.

A little positive feedback and appreciation for the organizers has the potential to go a long way, so that they have some additional payoff for continuing to deal with the tedious logistics.

Plus, karma stands for a thousand different things already. Adding one more meaning to the list doesn't make much of a difference with such a conflated concept.