If a CommentStoreComment is constructed without a Message argument, then
the RawMessage it uses instead should specify the comment text as a
plain-text parameter, not as a regular parameter: we don’t want any
syntax in the text to be interpreted at the Message level.
Change-Id: If14debde2bceae695c8955604ee96bd5005d8b66
Revision (or more accurately, its upcoming MCR replacement) should allow
for the full flexibility of CommentStore in its interface, and the most
straightforward way to do that is to use CommentStoreComment. But for
that to work sanely, we need a non-@private way to create a new
CommentStoreComment that hasn't been saved to the database yet.
Change-Id: I76028e8ef3da4568a16e098cdfbc806a67b814e3
