It may have been discussed by someone as “desirable” but I don’t believe there is any software that can handle this. Most will ignore the first part and only use the second.
As for the rest, it’s personal choice.
Also important to note that _MARNM is not correct. Popular, yes, but GEDCOM says use “TYPE married” instead. With the likely move to GEDCOM version 7 sometime in the future the “correct” solution looks likely to become standard in most, if not all, software.