The trust levels are explained in the FAQ pinned to this forum.
- Visit the Forums on 50% of the last 100 Days
- Read 500 Topics created in the last 100 Days
- Read 20,000 Posts created in the last 100 Days
- Like 30 Posts
- Receive 20 Likes
- Reply to 10 different Topics
- Don’t have more than 5 Spam/Offensive Flags
- Don’t be suspended in any Blizzard Game or Forum
The following info is from Discourse itself.
Trust Level 3 — Regular
Regulars are the backbone of your community, the most active readers and reliable contributors over a period of months, even years. Because they’re always around, they can be further trusted to help tidy up and organize the community.
To get to trust level 3, in the last 100 days…
- Must have visited at least 50% of days
- Must have replied to at least 10 different topics
- Of topics created in the last 100 days, must have viewed 25% (capped at 500)
- Of posts created in the last 100 days, must have read 25% (capped at 20k)
- Must have received 20 likes, and given 30 likes.*
- Must not have received more than 5 spam or offensive flags (with unique posts and unique users for each, confirmed by a moderator)
- Must not have been suspended or silenced
* These likes must be across a minimum number of different users (1/5 the number), across a minimum number of different days (1/4 the number). Likes cannot be from PMs.
All of the above criteria must be true to achieve trust level 3. Furthermore, unlike other trust levels, you can lose trust level 3 status . If you dip below these requirements in the last 100 days, you will be demoted back to Member. However, in order to avoid constant promotion/demotion situations, there is a 2-week grace period immediately after gaining Trust Level 3 during which you will not be demoted.
A lot of the activity can be monitored through your own profile.