[XiZa]

Also, the command syntax could possibly be made better?

Does vbulletin allow usernames that are numbers only? If not you could check if integer, its uid otherwise username.

Another error in the help:

/pm uname "userid"

should be "username"

I just checked and it doesn't appear that vbulletin blocks integer names..

Better syntax could be:

/ignore username
/unignore username
/ignore userid uid
/unignore userid uid

So only use a parameter (uid) to the more advanced option which I doubt many people will use anyway.

Don't require " " around the username unless there are spaces in the username. (then you could show an error mesage before sending the command to the server)