Inline, account-synced private nicknames for arbitrary users (Signal-style)

In pseudo-anonymous, privacy-conscious spaces (such as self-hosted union instances), members intentionally operate under public pseudonyms. While profile notes exist, they are buried inside the user profile modal and require clicking into each person individually. This makes scanning member lists or fast-moving chat channels impossible. Additionally, requiring mutual friend requests to solve this is a non-starter; it exposes social graphs, clutters contact lists, and requires mutual opt-in just to track who is who privately.

Allow users to set private nicknames for any user that sync across platforms and display inline, mirroring Steam's/Signal's approach:

• Inline & Distinct Display: Render the private nickname directly beside the user's public display name in chat messages, member lists, and reply previews (e.g., Pseudonym (Real Name)), rendered in brackets and a distinct or muted color.
• No Social Coupling: Can be assigned to any user from their context menu or profile card without sending a friend request or requiring mutual approval.
• Account-Synced but Confidential: Stored as private user-account metadata. It syncs across Desktop, Mobile, and Web, but is strictly client-facing; never broadcast to the target user, channel, or server admins.
• Search & Mentions: Autocomplete and user searches index against both the public display name and the private nickname.

Why Profile Notes don't solve this: Notes require an active click-to-open workflow on every single profile card, which breaks conversational flow. Glance-able, inline identification is great accessibility wise when reading chat logs. Precedents:

• Steam: Custom nicknames display inline next to profile names in friends and chat lists using bracketed, distinct formatting, syncing across desktop and mobile.
• Signal: Local address book names override or supplement public profile handles directly in conversation threads.