When the html rollout occurred, bbcode was stripped and replaced for forum posts.
It appears that bbcode wasn't stripped from quoted posts. Not sure if there's anything you can do about this but reporting in case this wasn't intended.
Example:
https://www.torn.com/forums.php#/p=threads&f=2&t=16390086&b=0&a=0&start=40&to=24582129
Post:
Quoted post:
Mentions: RW Quiz - Competitive or Termed?