* All 5 commissioners vote to seek public comment on rule * Two Republican commissioners have some reservations * Draft rule would allow for 'reasonable' net management * Public comments accepted until Jan. 14 * Telecom firms worry rule would hamper network management (Adds vote by commissioners, quotes, background) By John Poirier and Sinead Carew WASHINGTON/CHICAGO, Oct 22 (Reuters) - U.S. communications regulators voted unanimously Thursday to support an open Internet rule that would prevent telecom network operators from barring or blocking content based on the revenue it generates. The proposed rule now goes to the public for comment until...