Given a StringComparison instance, how should I check if it is case sensitive?
Should I compare it to all currently known case sensitive values in the enum?
StringComparison sc = ...;
bool isCaseSensitive = false
|| sc == StringComparison.CurrentCulture
|| sc == StringComparison.InvariantCulture
|| sc == StringComparison.Ordinal;

Yes, for the enum form (StringComparison) that's fine. MS is incredibly unlikely to add another StringComparison value now, given that adding a value to an enum is effectively a breaking change.
For a StringComparer, it's rather harder :(
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