If I use
[tag:debian] almost anywhere on the site I get something like this: debian
This, however does not work in the excerpt text of a Tag Wiki. See an example here: debian-squeeze.
I'm pretty sure this is intentional. The Excerpt shows up as a hover-box and the tag-style would be out of place in that box. The body of the tag-wiki can certainly use it though.
After some research, this has been brought up on M.SO before. Specifically: