[GuidoK]

If you wanted to use m for a thousand, you should have used the captial M as Latin only knows captials.
But for roman use you cannot use 130M as in 130.000
you either use Latin numbers, so that would be CXXX (there should be a bar above the letters, but I cant type that: C for Centum milia, X for Decem milia), or you use the SI prefix system (like the rest of the world).
The SI prefix system dictates that k=kilo=thousand.
The accountingcoach is a very trivial information source imho...
The SI prefix system is certainly the most used system to abbreviate large or small numbers in the 10x scale (and there m is 1/1000 and M is 1.000.000

But hey, if you want to rule out confusion 100%, just write the whole number.
It's certainly most confusing where everybody in the whole thread uses k as a thousand multiplier and there have been quite a few (so si-prefix).... and you use another...