Users have reported that accounts without an active Premium subscription can no more comment on channel posts or send messages in groups on behalf of a channel. A close source to the Telegram development team talks about that decision this way:
“Since the introduction of this feature, it has been difficult to assess the scale of the scams made.
80% of the comments made and messages sent on behalf of channels were identified as spam. Previously, channel and group administrators suggested removing this feature entirely, but instead of that, we have limited it to those who have an active Premium subscription. Hopefully, this will reduce the spam operations that take advantage of this feature, without having to entirely drop the feature.”
