Well, there goes any hope of a sensible case-insensitive way to compare strings in German. Unless you can figure out which of those two should correspond to "ER TRINKT IN MASSEN".
I think drinking too much is why we are having this problem in the first place, so maybe people should just stop it. You'd end up with Maßßen and Maszen eventually. Ich geh dann mal zum Arz, mir jezt ein attezt holen. Da wird man doch bekloppt.
I maintain that ss is a legitimate substitute in standard German orthography, just as ae for ä etc. not only because I can't be arsed to switch key layouts, but because ß is a useless character. If you compare Fuß, Ruß and Mus; Muss and Bus, Plus; Museeum and Muster. It is derived from a ligature, which is not any less confusing between ss and sz. So Buße implies it was once written Busse (or Busze). Add to that the phonetic difference between jetzt, jezt, and Arzt, is rather ridiculous, I mean, what do we have the c for? We rather standardize an extra letter and use c chiefly in ch and sch, but why? Ich habe da so meine Cweifel, ehh Tsweivel, eh ... ach lassen wir dass.
But that function would not be toLower(), it would be toSwiss()
> unless someone can come up with a string where replacing ß with ss changes the meaning
"Er trinkt in Maßen" - He drinks with moderation.
"Er trinkt in Massen" - He drinks huge amounts.
The pronounciation is different, too, a vowel before "ß" is long, before "ss" short.