This is a really weird bug with the server address in the add server menu. It somehow does not correctly deal with dots. Please note that the "Direct Connect" menu is not affected by this bug. Use it to verify that this is a bug.

Steps to reproduce:
1. Go to "Add server" in the multiplayer menu
2. Type "example.example.com" (without quotes) as the server address
3. Try to remove the second "example" while keeping ".com" intact
4. Notice that you will be left with "example.e.com", unable to remove the e
5. Try to remove the first "example" while keeping the first dot intact
6. Notice that you will be left with "e.e.com", unable to remove the e again
This is another variation of the bug:
1. Try to type ".example" as the server address
2. Notice that you can't type anything after the dot