How a community chat platform models its data: servers with nested channels, roles carrying permission bitfields, three-state per-channel overwrites, per-server nicknames, messages and threads, reactions, attachments, invites and voice sessions.
How a webmail service models its data: labels applied many-to-many instead of IMAP folders, one stored copy per message, conversation threading, attachments deduplicated by content hash, delivery filters, drafts, read state, spam scoring and quota.
The phpBB and Discourse shape rather than the Reddit one: curated categories and boards, threads bumped by replies, flat numbered posts with quoting, reputation and badges, a report-driven moderation queue and private messages.
How a team chat product models its data: workspaces and per-workspace identity, public private and shared channels, a read cursor per member instead of a read flag per message, thread replies, mentions, files, saved items and installed apps with granted scopes.
How a mobile messenger models its data: accounts keyed by phone number, linked devices, private contacts, direct and group chats as one entity, messages with media and replies, per-recipient delivery and read receipts, and disappearing messages with a TTL.