I don't know for sure...Other than the Officer's Mess (the location of which I'm now aware of thanks to this post
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), I've noticed several other mess halls. There's a Seamen's Mess forward on C deck (port side) which says it seats 35, a Firemen's Mess starboard on C deck that says 87 seats, and an Engineer's mess on E deck (doesn't say how many seats), so best I can tell, different types of crew members maybe ate in different locations in the ship? Those were the only mess halls I found on a quick look over the
deck plans, so there may be others that I missed.
As to ranks for the crew, I know there were some higher ranked crew members in the different departments (like a leading fireman, chief engineer, second engineer, junior second engineer, junior assistant second engineer, and several others in the engineering department detailed more in the list of crew members and their duties aboard ship) but as best as I can tell, they ate with the rest of their department (ex, engineers in engineer's mess). I don't know, and I'm curious if anyone has any more information! I'd be happy to hear if anyone knew anything else.
I'm also curious to know where crew members whose jobs were things like window cleaner, lamp trimmer, and the lookouts or the postal workers ate. Do they count as "seamen" and would they eat at the Seamen's mess? They're listed in the deck department along with the able seamen, who I assume would eat in the Seamen's mess. Or maybe I'm just missing another location of a crew member's mess somewhere on the ship's deck plans...
Also curious about where the pursers and such would eat. I've heard the Chief Purser (Hugh McElroy) did regularly dine with passengers.