If you create a new tag with an accented character, it gets converted to an un-accented character. For instance:
pokémon → pokemon
But when you search through this site's search box, the accented character is deleted. So when you search for
[pokémon] in the search box, it is converted to
[pokmon]. There should be consistency with this.
There was a feature request for this in Meta Stack Exchange, and it was marked as "status-complete" in 2012 and indeed it looks like it's working fine on that site. A mod noted that it would be rolled out in the next version. I'm not sure if it never made its way to Gaming Stack Exchange, but I see no reason that this shouldn't be intended behavior for our site.