we could do with a grammar for tags

The spec says 'The name of a tag MUST not exceed 255 bytes', but doesn't specify an encoding, so that doesn't make much sense as it stands.

Should we allow non-ascii? (they are used as display names, so potentially) Spaces? Are they case-sensitive?

They are specific to users so homograph attacks aren't too much of a worry.

Review the tag requirements in the Matrix specification, focusing on the 255-byte limit and the unresolved questions about encoding, non-ASCII characters, spaces, and case sensitivity. Done means the specification documents a decided tag grammar and its validation rules.

Written by the indexing model from the issue text.