User blog comment:Toughpigs/Wikia's new Forum demo/@comment-26686429-20120726004959/@comment-10370-20120726210704

Highlighting a thread means that every logged-in person who visits the wiki gets a notification, if they visit while the highlight is active.

Highlights automatically expire after 30 days, or an admin can turn the highlight off at any time.

You don't get Highlight notifications cross-wiki -- so if I've highlighted a thread on Muppet Wiki, you won't see it unless you visit Muppet Wiki while the highlight is active. You won't get it just because you've edited or visited the wiki before the highlight was turned on, or after it's turned off.