Replying to myself (can't edit anymore), looks like the W3C spec bungled it in your [1] by referencing "atext" from the RFC. For example, as specified it disall

Replying to myself (can't edit anymore), looks like the W3C spec bungled it in your [1] by referencing "atext" from the RFC. For example, as specified it disallows addresses with periods in them. In the RFC, "atext" is just a building block in the syntax of the local-part before @ sign.