Reading Level

I think <link rel="alternate"> would be something we'd want to use for this. However, there isn't a mechanism to express varying reading levels. We might want to suggest creating such a mechanism as feedback. I can think of two approaches:
- Define that the "title" attribute, when used on <link rel="alternate"> provides human-oriented information about the nature of the alternate resource, and require that user agents make that value available to users when creating the hyperlink per the specification. Note however that rel="alternate" is also allowed on normal <a> links, and this requirement would possibly confuse the semantics of title there. Anyway, I'm cautious about overloading title.
- Introduce an attribute whose value can indicate reading level, or anyway things beyond MIME type, language, and device media type which are addressed by other attributes. I would expect a lot of resistance to this unless we submit an extremely well-considered proposal and get initial buy-in from mainstream user agent developers.
It is tempting to suggest using the <summary> element to provide a short version of a section. However, that element is restricted to a specific use-case of interactive widgets. It might be good to suggest a parallel feature that provides an in-line simpler representation of arbitrary content regions, that user agents show or hide by default depending on factors such as user preference, device size, etc. But again, I would expect a lot of resistance to this unless we submit an extremely well-considered proposal and get initial buy-in from mainstream user agent developers.
Possibly the ARIA "complementary" role could be used to provide an inline easier-to-read summary. However, the use case is more generic and it might overload it to suggest it be used for this.