Could you expand on the operation of the UART transmit behaviour (when not in network addressable mode) given in the data sheet, specifically the buffering (if any) of transmit data and also status bits relating to the transmit buffer/register being full empty.
Is the "transmit register", COMTX, equivalent to the "transmit buffer" referred to in Table 96 and 99?
It would seem that writing to COMTX clears TEMT bit in COMSTA0 and also sets bits 2:1 of COMIID0 to '00'.
If there is no buffering of data between writing to COMTX and it being sent from the SOUT pin then that only allows the duration of any parity & stop bit(s) framing to reload COMTX before a delay will be observed between the transmission of bytes.
Do any status bit(s) indicate that the data has been actually sent (including stop bits) from the SOUT pin?