[falsedan]

This is gatekeeping, since the message is coded to be obvious to those "in the know" (of course mb means mebibyte!) but is a barrier to those who are trying to learn more (mb probably means megabits per second? it's a unit for measuring download speed? why is the 's' left off?)

This is putting the burden of collaboration in the wrong place: it shouldn't be a question of, can we expect a reasonable engineer in the industry to understand this unambiguously (with some deductions); but rather, can I hold down the shift key when typing the abbreviation for megabytes.

Obviously this depend on the actual audience, don't bother following this in team chat where speed is more important than clarity.