I’m not sure how automated this could be done, but a feature that tags threads/posts with the glyph/character discussed would be very helpful. For this to work, you’d have to be able to search the forum with one character only (now you need minimum three). Special characters should also be supported.

Examples:
A search for “&” should return all the threads/posts concerning ampersands.
A search for “z” should return all the threads/posts concerning z.