Why are user Trust Levels not listed by the names of all users?

[Moin]

Plugin Author is not a trust level. It is a title. Badges can be used as a title when Allow badge to be used as a title is enabled. This is the case for the plugin author badge.
Titles can also come from groups, like @community-moderators or they can be given by admins directly.
If you want every trust level as a title option you can enable them for the associated badges.

Automatic titles from trust groups

Just modify existing badges, “basic” and “member” and be sure to enable the setting Allow badge to be used as a title (regular and leader can already add the relative badge as a title). Users (if they want) will be able to select the title on their user profile.