As of recently, tags can now be any (Unicode) character (not just 7-bit alphanumeric characters), with that feature being turned on only for sites that request it: and that request must be well-thought-out (viz, must include a plan of how the feature will be used).
Do we want this feature? If so, what shall we do with it? Please post propositions as answers here so that others may up- or downvote them.