Keybase UIDs

The Keybase developers have UIDs attached to their OpenPGP certificates which do not contain their name but their Keybase profile URL without protocol.

These look like this:

```
keybase.io/max (v0.0.1)
keybase.io/chris
```

As they are the developers, they own the keybase.io domain. Therefore it is likely that they actually have email addresses set up at these locations. Now I noticed other people having similar UIDs.

Like this:

```
keybase.io/someuser
```

Is there some kind of documentation about the meanings of this? Or can users actually have a mailbox at Keybase. Maybe this is just a user copying the behavior of the developers without knowing why? If so, is it still recommended to have such a UID? Without an email address part maybe?

Start with the Keybase UID examples in the issue body and determine the documented meaning of the profile-style UID and email-like suffix. Done means adding or updating documentation that answers whether these addresses are mailboxes and states the recommended UID form.

Written by the indexing model from the issue text.