When viewing a discussion, you'll notice that the URL is typically appended with #latest.
In this case, the #latest at the end of the URL refers to the "latest" or "most recent" page of the discussion for the user who is clicking on it.
- If User A has read everything, they'll land on the last page of comments
- If User B has read up to page 3, they'll be taken there
- If user C hasn't viewed the discussion, they'll be taken to the beginning of the thread
You can try this out with a test user or by using an incognito window (if your community is public).
If you would like to turn off this feature, contact Vanilla Support.