Comments (even wall posts are just comments) use just a rudimental version of features. Just smilies and URLs will be displayed – and text, of course – but no other code format.
Would be helpful to tag someone else to a wall post. Let us assume I was talking about you, Black Rider on let's say for example on Alexander Ebert wall. Rather than having to send your a PM to clue you in, it would be a lot easier to tag you and draw your attention