I sent you questions @PhilMcIntosh and a couple extras to Discourse - here is the response: ( I don't know why the ""can it be blocked"" got cut-off and I'll follow-up on the comments under topics)
Does anyone have experience converting a Socialcast site to Discourse?
**Yes, we have an existing import script.**
Can it be configured to show comments under each topic instead of having to open the topic in another page?
I'm not following here sorry. Can you elaborate?
can it be blocked
Yes, you can blacklist crawlers or put your forum behind a login.
Can account signup be made invitation only, not public?
Yes, absolutely.
Is there 2FA options for login?
There sure is.
Can a member be part of some groups but not all?
Absolutely.
Is there a calendar feature?
There is an events plugin (note that this would incur a monthly fee to have installed as it is an unofficial plugin).
Is there a group broadcast feature?
You can pin announcement banners is that what you mean?
I see a mention of file storage and wiki, but I can't see how to access them in the demo online
File storage simply means that we allocate you space to store files that are uploaded into topics and posts. Any post can be turned into a wiki post, categories can be set so that all posts are automatically wikis, and you can configure your settings to allow all or some users to contribute to wiki topics.