The diamond with information you're hypothesizing would have been dug up and modified by that prehistoric civilization, only to be put back under ground. Otherwise, it wouldn't have been found in a diamond mine.

And would you trust (very) future civilizations to come across a small diamond and think: hey, I'm going to fire a laser through this thing in a particular sequence and interpret the outcome as UTF-8? I think anyone who wants their data saved for posterity would give that some thought and not leave it to chance.

> Otherwise, it wouldn't have been found in a diamond mine.

After 50k years, a library would become a diamond mine.

It's trivial to include macro structures that invite investigation, and utf8 is irrelevant. It doesn't matter what encoding scheme you use. utf8 is fine. All that matters is that there is structure.

For some reason, I imagine most diamonds just store the same word over and over:

HOT HOT HOT HOT HOT HOT....

Or, "under pressure, da da da da-da dum dum"

Another reason for using synthetic diamonds for jewelry.