Sorry for the inconvenience! Sounds super frustrating! I can see in the thread that your 4th attempt was successful (I can see your reply), but it definitely shouldn't be that difficult. The permissions for your usergroup should definitely allow you to reply in your own threads (see pic), so I'm not sure what else might be happening here. I'll try running a couple rebuilds in the backend to see if it offers any improvement. Let us know if you notice any change.