If it was about defederating with other people I would agree, but if it's a bad faith criticism of the instance I am also a part of, it's essentially about me. If someone is openly talking shit about my house from next door because they are upset about not getting their way in some petty dispute they participated poorly in with someone in my building, it feels fine to me to chime in and say what I said. Again, the rules of reddthat community support don't say it's just for locals (unless I missed something), and by the nature of federation it would be assumed that others can see and comment on any of these posts. If your support channel is supposed to be only for users if the instance, that could be a good change to make.