Yes, I too enjoy ‘Meet Up’ as a source for shared interests & activities.
Sincerity however, like trust, it is revealed in it’s own good time.
It often takes awhile, sometimes several years to really get the low down on anothers personality traits and how they show up in different situations.
There is no way to predict from a few casual meetings the sincerity of another.
It’s a gamble, as are all relationships.
If, after a few weeks or months you are observing any inconsistencies with a person, see any manipulative behaviors or see too much drama in their lives, well…these are the deal breakers for me and, unfortunetley, it is all about investing enough time to see the truth of a person beyond first impressions.
Good luck in your search for a new pal!