[AriaNotify] Should notifications be HTML rather than plaintext or SSML?

[minorninth]

It feels like a missed opportunity to invent a new API that's built around plaintext, or a speech-only markup language like SSML. I'm fine with not prioritizing braille in v1 but I don't think we should build an API that's not rich enough to support rich notifications in the future.

Screen readers already don't just read the text of the web as plaintext, some screen readers support things like:

• Inline markup like bold/italic/emphasis
• Pronunciation hints (CSS speak-as)
• Different output for speech vs braille
• Math
• Abbreviations
• Various markup to distinguish between phone numbers vs math, etc.
• Switching languages in the middle of one sentence

More importantly, these are all web features (HTML, CSS, etc.) - and as they're added to web standards, browsers and screen readers can adopt them to provide richer speech and braille output.

Do we really want to move to an API that leaves out all of that potential? Do we want to say that we're never going to have an API that provides a way to annotate whether something is a phone number or an equation, or stresses one word - or that if we're ever going to support those that we'd have to reinvent them, rather than building on existing support for reading HTML?