Telegram is just like reddit in this regards. Its up to the user to make and enforce content rules in a closed community. If you want a channel/group with only

Telegram is just like reddit in this regards. Its up to the user to make and enforce content rules in a closed community. If you want a channel/group with only very specific content then make it somewhat hard for stupid people to gain write permission and have a bunch of volunteer checking the content submitted. Every other platform would require similar strategies to get what you want. The existence of other groups/channels on telegram with other rules is completely irrelevant. If people are unable to switch between communities and respect the different rules in each then that's their problem and you just remove them.