Character name unusable after server transfer.

[Nekodar]

At the time of transfer your character was flagged as there was already a character with that name on the target world.
That flag is not removed until you change name.

Essentially, you prevented yourself from keeping your name by doing this.

I'm not saying it's not an issue, but this is how it works.

[Mytenia]

Once the transfer was done, I log in my account and deleted the character that I had made in Ultros to reserve the name, so that it would default to my old character that I just transferred... and it did.

This is where you did it wrong.
You should have deleted the reserved character just before the transfer,not after.
Like said above,you flagged yourself with a same name character and even if you delete the second one after the transfer,the transfer script had already flagged you're good character for a rename since it saw the other one before you deleted it.