How to get someones youtube account suspended?

There is this person who is impersonating another youtuber (exact same username but with a "1" on the end and same profile pic) and they are spaming their wall and writing rude comments (so people think that its the original youtuber writing all the rude things.) i have reported all the comments and wall posts as spam but they just keep writing. they dont have any videos so i can't flag them.. anything i can do to report them?