fletcher on 20 Mar, 2017 02:10 PM
My apologies -- going through email and realized that I never replied to this.
As you may or may not be aware, I have been hard at work on MMD v 6 for quite a while, and it is nearing completion (for 6.0.0 anyway!). I have made an extensive rewrite to the support for abbreviations, acronyms. However, I am not sure that specifically supporting plurals is the way I want to go.
I recognize the utility of this function, and understand why its included in LaTeX, which is definitely an "everything but the kitchen sink" sort of program, which is why it is so powerful and useful.
MMD, however, is (in my opinion) powerful and useful as much for what it does not include as for what it does include. I was on the fence about abbreviation support to begin with (though I use them on occasion myself now). But I think supporting specific plural forms is perhaps getting a bit too specific for the vast majority of users.
For now, you are correct, that raw LaTeX is one option (though not specifically supported in MMD-6 yet -- see the issues page for details). A second abbreviation is the other.
A different approach, that might be more useful, would be a syntax that indicates that an abbreviation should always be used in the abbreviated form?? In other words, every use of that abbreviation is a "subsequent mention." This would allow the plural form to be specified as a separate abbreviation, but without triggering another "first mention." I'm not sure if there is a precedent for such a thing in LaTeX already or not.