OK, that time it posted the edit, but left the message in the editor.
Trying a new post with the link (even HTML-encoded) gives the original result - the message is not posted, and is left in the editor.
Loading User Information from Channel 9
Something went wrong getting user information from Channel 9
Loading User Information from MSDN
Something went wrong getting user information from MSDN
Loading Visual Studio Achievements
Something went wrong getting the Visual Studio Achievements
OK, that time it posted the edit, but left the message in the editor.
Trying a new post with the link (even HTML-encoded) gives the original result - the message is not posted, and is left in the editor.