New users (and old users returning to the new forum platform) will notice that they are limited as to what they can do when they first log in. Here is an excerpt from the Discourse documentation explaining this:
New User Sandbox and the Trust System
If your discussion area is be open to the public, new visitors will arrive that are initially strangers to the community. Discourse has a trust system where users can, over time, earn the trust of the community and gain abilities to assist in governing their community.
Discourse is designed to offer safe defaults for public communities, even with no active moderation.
0 (new) → 1 (basic) → 2 (member) → 3 (regular) → 4 (leader)
All new users start out in a sandbox with restrictions for everyone’s safety. Trust level 0 (new) users cannot …
post more than 2 hyperlinks
@name mention more than 2 users in a post
Every action a user can take is rate limited for safety, and especially so for new users. But don’t worry, new users can transition to trust level 1 in about 10 minutes of reading.