Ok. I think I understand. I also see now why it seems confusing. It's not very intuitive that the initial `!` doesn't just mean "tag", it means "local tag", unless that is if a `%TAG ! foo` directive has been used. Then they are transformed into "domain tags" without any initial `!`.

In other words, when someone sees something like:

    --- !foo.org:person
    name: Tom

They think that's a domain tag b/c it resembles a domain tag. They do not realize it needs to be.

    --- !<foo.org:person>
    name: Tom

In hindsight this was probably one of the arguments for using `!!` for local tags instead of `!`.