Findbugs is another option. Also most IDEs will issue a warning for this by default, and you can configure them to consider it an error rather than warning, to make it easier to find this sort of thing. [ December 03, 2008: Message edited by: Mike Simmons ]
Well, Findbugs will never see the comment, since it operates by analyzing class files, not source. And in IntelliJ at least, it's possible to configure the inspection to either consider a catch with only a comment to be empty, or to consider it non-empty. The latter is the default, which I think is reasonable. Few people would bother to comment an empty catch block unless they're explaining why an empty catch block makes sense in this case - which shows they've at least considered the issue. If you don't trust the judgement of the coders who might have written such comments, then configure the inspection to ignore them, and can review each yourself.