From HTML WG Wiki
There has been a discussion of potential need for a specification that would allow browsers to include a Rich Tech Input Control; e.g.
Note HTML5 has contenteditable="" for this.
Without further evidence/research, it's not clear that this is an issue that merits attention of the HTML Working Group as a whole. The discussion didn't cite any specific text in the spec that should change, nor did it introduce reasonably complete example/test cases. See IssueTemplate for further advice on raising issues.