The takeaway shouldn’t be “strings are hard”. Strings are hard, but that’s not the problem here. The problem is using inappropriate data types for the task at hand, and the takeaway should be that representation matters.
Representing an IP endpoint as a string only really makes sense at the human-computer interface. In general, the first thing a program should do with such a string is convert it into a more suitable data type. And as noted elsewhere, more often than not there will already be a library function to do so.
Strings are especially pernicious because they are ubiquitous, in that just about anything can be represented as a string, but the operations one can do on a string representation of an object do not generally correspond with the operations one would want to do on the object itself. This disparity is the source of many bugs, which the article exemplifies (though falls short of directly addressing).
Similarly problematic are assumptions that converting an object to a string and a string to an object (i.e. `parse` and `format` functions) are bijective. This is not generally the case. (Wise practitioners might choose such a mapping, though, when the opportunity presents.)
Edit to note: I store the fully scoped IPv6 address in a database as part of my CMDB mechanism.