Unclear character set constraints and non-UTF-8 html

[himorin]

Section 6. Links is not clear and unorganized on several points:

1. Link relation type is strongly connected with media types as constraints, but these mime types have additional constraints to these, which results in scattered descriptions and writings of specification.
2. Constraint for service-doc link relation type is written as

human readable documentation, supported formats are Unicode Text, markdown, HTML and PDF.

but wording Unicode is not clear. Considering restrictions placed at mime types, it should be clearly stated with UTF-8 is mandatory over all applicable types.
3. hreflang is marked as optional, but should be mandatory for text/plain, text/markdown, and possibly on text/html.

We would propose to rewrite this section into one table for clarification and ease for noticing all of constraints with reorganizing all of attached text for description totally, something like:

Relation-Type	Supported Media Types	Constraints	Remarks
icon	image/png, image/jpeg
service-doc	text/plain, text/html, text/markdown, text/pdf	Linked files MUST use the UTF-8 character encoding. hreflang is mandatory for text/plain and text/markdown	Human readable documentation.