A new forum_blog switch on channels (off by default), turned on and off
through the same channel permission toggle as Forum mode and NSFW, so only
someone who can change the channel's settings can flip it. The channel list
carries it.
With it on, a topic belongs to its author. A reply in the topic's thread is
part of the post when the topic author's own account wrote it (and it is not
a bot or relayed message); everything else is a comment. Nothing is stored
per message, so turning it on or off needs no migration and changes nothing
on disk. The rule lives in src/forumBlog.js.
The server works the answer out and sends it: thread history marks each reply
post_part and says the topic is a blog post, a new reply carries post_part,
and topic cards and live thread updates carry a comments count alongside the
reply count. user_id comes from the signed-in socket, so nobody can make
their reply count as the author's, and bot replies are always comments.
ancsemi