Companion to
楼主 (LZ, 'thread starter'). In the BBS-as-building metaphor, each reply to the OP is a
楼 ('floor'); when someone replies to that reply, the conversation tree branches off, and the original replier becomes a
层主 ('floor-owner') — the host of that sub-thread. Common on Tieba, Zhihu, NGA and similar forum platforms.
