Pinning messages at the bottom of a page

More details about this request: having a way to pin a message permanently to show up at the bottom of a certain channel or have the member dismiss a text box with a custom message such as "Make sure to read x" before being able to chat in that channel can come in handy in a lot of situations.
For instance, in a project collaboration channel where people can join or create a team, a template is really important for the quality of their posts. Things need to be clear and organised and it offers the minimum information someone has to give to others about themselves/the team and project. The problem is that a lot of people don't notice that a good template is needed and there's no way to let them now beforehand with the current existing features.