The Comment Support Tips panel appears at the top of the screen at the point when the participant hits "Submit" for his/her comment. The goal is encouraging a moment of reflection about whether the comment can be improved. The participant is given the choice of either editing the comment or submitting as is. The database stores the initial version of the comment, so you can assess the effect of the Tips.
The default setting presents the Tips when the participant submits his/her first comment. After that, the user can open the Tips by clicking the Comment Tips button above the comment box. (This button is not shown until after the automated presentation has been triggered once.) You can change the setting to present the Tips before submission of every comment. See the SmartParticipation Manual. Be aware, however, that users may be annoyed by the constant interruption and simply stop commenting.
In general, the Tips should be concise and to the point, to increase the odds that participants actually read them. Include an attention-grabbing lead-in sentence; a small graphic can also be added to increase visual appeal. Think about the likely level of commenting skills of your anticipated participants and try to focus on what would most improve discussion at that level of participation literacy.