Cancelling the two blanks rule has been suggested (on the grounds of different markers breaking a list, no less), and a “list break” syntax has been proposed, which would be consistent with hard line breaks:
Two lists:
1. item
2. item
\
1. item
2. item
(although those are ordered lists, the particular list type is unimportant).
CommonMark.NET already holds these (as well as other) data as part of the syntax tree and its (non-XML ATM) AST format.