This dialog box is used to set the comment delimiters used when reformatting text. Typically this happens when you use <Ctrl-F>or the Comment or Comment box commands on the EditText formatting submenu.
"CRiSP is awesome, especially for anyone who likes to use Brief on the PC, and hates vi. I use it for all my code development and maintenance tasks. It's also great for editing binary files or very large files, or files which have very long lines, which cause other editors to choke."