If you truly believe it is a bug we should be contacting mod_security to fix, please submit a bug report. If you did already submit a bug report, you are welcome to respond to that bug report ticket (those go to http://go.cpanel.net/bugs
rather than the regular ticket queue) and mention that you'd like to request if we can contact mod_security about the issue.
It is a flaw with mod_security in conjunction with mod_ruid2 and not with cPanel itself. Some components do not work with other components and, typically, we end up disabling those components when the other is selected. For example, we disable FrontPage and mod_mono when mod_ruid2 is selected. What I foresee happening if it isn't going to be fixed by mod_security is that we might end up disabling the option to even pick mod_security when using mod_ruid2 (if people feel this error is sufficient to make it unusable).