vim voldmarker with a space

'foldmarker' 'fmr'    string (default: "{{{,}}}")
            local to window
            {not in Vi}
            {not available when compiled without the |+folding|
            feature}
    The start and end marker used when 'foldmethod' is "marker".  There
    must be one comma, which separates the start and end marker.  The
    marker is a literal string (a regular expression would be too slow).
    See |fold-marker|.


but if I use this:

:set foldmarker= {,}


I got E536: comma required: foldmarker=


why space not supported?


then how do I fold with {,} but exclude the {6} ?

    policy COMMIT_TRAP {
        events ui_commit;
        attributes-match {
            ui_commit.username matches "{6}";
        }
        then {
            raise-trap;
        }
    }


thanks!