[sirobg]

A lot of good points here, thanks a lot!

> Email-chain would be the easiest.

It would require users to share their emails to meet.hn, am I right?

> creating a some form of very simple forum board

Might be a good idea as well. It would require more work and maintenance but could be valuable.

[glenneroo]

Possibly unpopular here but how about a Discord server with a channel for every city? When you join Discord, a bot could ask which cities you want to join (allowing people who travel to join multiple cities, but maybe limit it to some sane number to prevent bots from trawling everything).