>>/5566/
1. Log in
2. Look for "Always use role signature" in "Settings"
3. tick the checkbox
4. ???
5. PROFIT
Alternatively add #rs into the name field.

 >>/5572/
It's a board setting, gives minor protection from flooding with the same image.

 >>/5575/
Magrathea doesn't have alerts.
The backend is the same, the frontend different.

 >>/5576/
I don't think I ever seen that error.

 >>/5578/
A hash is generated from the uploaded file which is matched to the file hashes stored in the database. It's done so the same file doesn't get stored on the server over and over. And ofc, used for the r9k prevention too.