A) typeparamref == paramref, just for generic type arguments. So whereever paramref is, typeparamref should be too.
B) That sounds about right, the CommentParser just parses the contents of the primary tags, which is a combination of plain text and support tags.
C) I'd make code a support tag.
As for how the output is getting to the views... Have you had a look at the PatternTemplateResolver? It's a rather badly named class that possibly has too many responsibilities, but it essentially expands template paths to output paths, and turns a list of Namespace's into an instance of ViewData for each output file. The ViewData is then passed to the HtmlGenerator which creates the spark view. The Namespaces come from the DocumentModel class.
D) My understanding is that value is a primary tag, but I may be wrong. I got it from
this page, which makes me believe <value> == <return> for properties.