I have BrownOut, there are no standard connectors for any RS232 standard I've found, only specification for one side being male or female. The use of DE9 and DB25 connectors is traditional, not a part of any standards based specification I have been able to find. Nor is there any requirements I'm aware of for it being full duplex, again based on standards, which I've been unable to find! The most detailed description I have ever seen of any RS-232 spec is electrical only. -3 +3 is the logic threshold. +/- 12 volt tolerant if not a bit more, short circuit tolerant, and some capacitance/resistance limits which basically come down to transmission line specs, the most commonly referenced one I can find is 20k baud is considered the physical limit. Those again though are probably from parasitic values.. Even if bidirectionallity is required software flow control can do that over two wires.
I'm really curious to see some hard links that define RS-232C standard Even TIA-232-F would be wondrous as that's based on EIA-232C which is as close as I've come to and that has no description of connectors and that's only from hearsay of the standard as you said I can't download the whole thing.