I'm far from my computer so I can't check how it should look.
Check if at Server.cfg you have set motdurl as "none" (not sure if this continues working, or it was already fixed. At least in the past having it at none worked, after restarting the server and a map change).
If I leave it to go to the Obsidian Conflict MOTD webpage it will still load and function normally. The only time it shows the HTML code is when the server reads "motd.txt"