it would be so helpful if there would be a discussion forum for stitch users to support each other.
We've launched the MongoDB Developer forums to cover this!
You might be interested in joining the official MongoDB Community Slack. I think the #stitch channel may be what you're looking for. There are quite a few channels where you can discuss all things MongoDB and get help from other community members. A good number of MongoDB employees, myself included, like to hang out there and answer questions as well.
To join, just submit your email address on LaunchPass and you'll get an email with an invite link: https://launchpass.com/mongo-db