Creately.com has created a plug-in to integrate with FogBugz. We're spoiled in that they and Balsamiq have taken the initiative and put in the effort to integrate with our software. We're not users of websequencediagrams.com, and don't have any data on how many of our users are using it, but would be happy to help out any fan of both FogBugz and WSD.com. Just visit us at developers.fogbugz.com.
I would love to have this in Gmail, too!
We currently don't auto-reply on spam issues or to the same address more than three times in an hour.
Can you let us know what criteria you'd want to not reply on?