Ask HN: Best platform to create a private community for 100-200 people?

'Best platform' is a very broad term. Best in what way? In terms of ease of creation/coding? In terms of features/stability/reliability/scalability? Or what?

Be that as it may, if you're willing to explore the CMS route, I can vouch for WordPress with BuddyPress (and a handful of other) plug-ins. Proven, stable, feature-rich, quick to deploy etc. I'd say definitely worth checking out.

https://wordpress.org/plugins/buddypress/

There's also Telescope http://www.telescopeapp.org/ if you want to build something more like a reddit-style community

Have you tried Slack or Discord? It really depends on the features you want to have and what you mean by "community"... Maybe take a look at Discourse too.

If you are looking for hn or stackoverflow like community with moderation built in,take a look at discourse. I have used it and really like it.