I tried to specify two special substitutions in my case feature:
ß > ẞ
ĸ > K‘
In Adobe’s enviroment ß becomes SS and ĸ remains ĸ, but OpenType-savvy browsers respect my feature. I understand there is some discussion re. the cap eszett, and I am not sure about the one-to-many substitution in regards to the old greenlandic k. Would it be better to leave these out alltogether? Are there other “hard-coded” case variants I should be aware of?