Why can't anyone see what I'm typing on channel?

One of several server features might be keeping people from seeing your comments.

The channel might be moderated using channel mode +m; if so, no one can talk who hasn't been explicitly voiced by a channel staffer via +v. You might want to send a private message to a channel staffer to find out what's wrong. Channel staffers are identified on most clients with an @ in front of their nicks.

The channel might have +R set. This mode prevents you from talking on channel until you're registered and identified to NickServ. In this case, you'll see a message in your server notice window which explains the problem and points you to NickServ for more information.