A:
First check your state's statutes.
Under my state's Open Meeting Law, a community may choose to allow public comment during an open meeting, but allowing it is not required.
RONR is silent about outside participation, but it does state (p. 476) that a board not a part of a society can adopt its own rules as long as they do not conflict with its governing rules such as state laws.
Therefore, it's possible your board can adopt a rule regarding the rights of non-board members.