An identity is the bot's concept of a viewer. Each identity can be associated with one or more service-specific display names (e.g. the bot knows that the streamer is referred to on Twitch [the service] as SwirlyEyedLink [the display name]). This concept comes in handy, for example, when needing to keep straight who's who between Twitch chat and in-game, since a viewer might have a different display name for each.
A service may be "connected" or "unconnected". A connected service provides its own display names to the bot, and therefore the bot disallows updating display names for those services. An unconnected service must have display names provided to the bot manually, as it has no other way to retrieve them.
Services currently recognized:
!identity aka Twitch:SwirlyEyedLink Switch:SELink
!identity create Switch:Squidding