[Sesse__]

It's why the Unicode Collation Algorithm exists.

If you look in allkeys.txt (the base UCA data, used if you don't have language-specific stuff in your comparisons) for the two code points in question, you'll find:

  004B  ; [.2514.0020.0008] # LATIN CAPITAL LETTER K
  212A  ; [.2514.0020.0008] # KELVIN SIGN

The numbers in the brackets are values on level 1 (base), level 2 (typically used for accents), level 3 (typically used for case). So they are to compare identical under the UCA, in almost every case except for if you really need a tiebreaker.

Compare e.g. :

  1D424 ; [.2514.0020.0005] # MATHEMATICAL BOLD SMALL K

which would compare equal to those under a case-insensitive accent-sensitive collation, but _not_a case-sensitive one (case-sensitive collations are always accent-sensitive, too).

[happytoexplain]

Are the meanings for the levels for each code point defined somewhere (accent, casing, etc)?

[Sesse__]

Typically it is defined by the collation. For the default collation, where all the weights are as in the file, it's none/accent/accent+case. But if you go to e.g. Japanese, you can have a fourth level of “kana-sensitive” (which distinguishes between e.g. katakana and hiragana).