[OSM-newbies] How to block a user for editing

[Xan]

Hi,

Perhaps it's not the best place for asking it. Today I found a user 
http://www.openstreetmap.org/user/sergiclar that simply invents highways 
for funning and the changeset comment he/she do is "a joke, please 
delete it".

I'm sending a message now for delete this edits, but if he/she don't do 
that, should we block that?
How to do that?

See the edits of this users and see the comments (spanish)

Thanks,
Xan.