How to remove some comments from a node?
Apparently, the comment metadata populated after node_load comes from comment_node_load(). But indeed the comments themselves aren't added until view time at comment_node_view(), which calls comment_node_page_additions() which adds the renderable comments, which calls comment_get_thread() to load the cids.

So perhaps it would take adding vid column to the comment table, and then adding vid condition in comment_get_thread...hmmm.