*** Overview - Describe the feature from an end-user perspective.
Getting a mouse-over on characters and bosses, just like the item-tags, on forumposts.

*** Functionality - Describe the feature from a development perspective.
Adding an option to add [armory] and [npc] tags to the PHPbb output and then adding those to said output would suffice. The [armory] tag is the easiest, just add [armory] in front of a character's name and [/amory] after it and that's it ([armory gearlist] in front of the char would be even better though).
For the [npc] tag you'd need the npc-id to give the right npc for 10, 25, heroic and normal I think. Adding [npc] in front and [/npc] after a boss's ID should do the trick.

*** Notes - Is there any additional information to provide regarding this feature?
I did make an example of what a normal TotC10 forum post would look like. It's a bit of a poor example, since the Faction Champions haven't got a page on WoWhead, so I removed those; the WoWhead page points to an ?object=xxx url. On top of that, with the Twin Valkyrs you'd have to pick one. :S
The top 2 chars have the [armory gearlist] tag, the others have [armory]. This clearly makes the [amory] tags my main requestt btw; [npc] tags might not be as easy as I first thought. :)
Link: http://www.vexillum-guild.com/forum/viewtopic.php?f=45&t=2994

*** Use cases - How would a user make use of this feature?
People that have the tooltip addon installed on their phpBB 3 would have the option to make even cooler and better looking posts. :)