Not sure why everyone's so prone to reinventing the wheel on this one; never saw anything wrong with

Sat Symbol - Support the design initiative to make this the universal Satoshi symbol. Open, free, and unrestricted as Satoshi would have wanted. Please share. Satoshi Symbol, Sats Symbol.

That it's not in unicode is less than ideal I suppose but that seems easy enough to fix. Alternatively, using n₿ for sats and μ₿ for bits seems straightforward enough. And of course, μ₿5.15 would be equivalent to n₿515. Though I guess the complicated part of this is that the American school system makes it really hard to understand the concept of prefixed measurements. Especially when one of the few places we all regularly use them (bytes) actually misuses the prefixes such that 1 kb may be 1000 bytes or 1024 bytes, depending on context. And to boot, usually is not clarified, but used to mislead for whichever marketing purpose makes the most sense.