$1 = 10 BTM
BTM is an abbreviation for "bitmill" which just needs to die. You don't say "that bug is 5 metermills long", or do you?
If it was a virtual bug i might.
When i use it i say "BTM" not "bitmill". I think it's a clearer distinction from BTC than mBTC. I think "i'll give you 20 b-t-m" is clearer than "I'll give you 20 millibitcoins" or "20 m-b-t-c".
People are not used to thinking in fractions, we need distinct units like dollars and cents, not fractional units like dollars and microdollars. uBTC and mBTC is particularly easy to mix up.
Except that "cent" is short for "centidollar", which means one-hundredth of a dollar. People already deal with these types of fractions on a regular basis, such as with my example about millimeters. I don't see anyone confusing meter (m) with centimeter (cm), millimeter (mm), micrometer (um), or even with kilometer (km). Each of those is unambiguous.
I do like "millies" and "mikes" as shorthand names for millibitcoins and microbitcoins. They sound personable.