I think there is a fine line between identifying yourself as a "Modder" and Identifying yourself as a "Builder". Both are enthusiasts.
You can be a modder but not a builder, these are people who do a lot of scratch builds and case mods, but your PC is full of bottlenecks, bad quality parts or ill-advised combinations of parts. Usually these people come from Autosculpting cars, people who work with metal a lot or people who paint things for a living.
You can also be a builder but not a modder, these are people who specialize in fantasy builds, they are familiar with what hardware it takes to run 4 titan blacks, they spend a lot of time in pc partpicker, these people are also very familiar with upcoming hardware releases. These people use standard cases and may not be comfortable with the first dremel cut.
Both are equal enthusiasts and both have their specialty, a Builder can ask a modder to mod his rig, and a modder can ask a builder to mix and match his parts to remove any bottlenecks.
Some of us are Builders, Modders and Overclockers.
Enthusiasts all the same.