I agree with the OP that the TL3 requirement is a bit harsh (it should not be so easy to drop to TL2 if you go on a 2-week vacation w/family), but Trust Levels and what privileges they come with are explained pretty clearly in the first post of the “new forum guide” pinned to top of General Discussion, so it should be easy to “makes sense” of how it works.
TRUST LEVEL 1
Get to trust level 1 by…
- Entering at least 5 topics
- Reading at least 30 posts
- Spend a total of 10 minutes reading posts
Users at trust level 1 can…
- Post unlimited topics and replies
- Edit wiki posts (more on Wiki Posts Below)
- Flag posts
- Create links and video embeds to trusted websites like Blizzard websites, YouTube, or Twitch
TRUST LEVEL 2
Get to trust level 2 by…
- Visiting at least 15 days, not sequentially
- Casting at least 1 like
- Receiving at least 1 like
- Replying to at least 3 different topics
- Entering at least 20 topics
- Reading at least 100 posts
- Spend a total of 60 minutes reading posts
Users at trust level 2 can…
- Have an increased “like” count.
TRUST LEVEL 3
Get to trust level 3 by…
- Must have visited at least 50% of last 100 days
- Must have replied to at least 10 different topics
- Of topics created in the last 100 days, must have viewed 500 topics
- Of posts created in the last 100 days, must have read 20,000 posts (both starting posts and replies)
- 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 (including forum suspensions or in-game account actions of any Blizzard game)
Trust Level 3 users can
- Create Wiki Posts (more on that below)
- Post animated gifs, images, compatible video embeds, and links to any website