Tangentially, if that callus was a plantar callus (circular with a painful point in the center), you can get sticky pads with salicylic acid from the drugstore that will gradually destroy it. Much safer than digging into your foot with a knife, but I'm glad to hear it worked for you!
The same, I suppose, as using Wikipedia to get an overview of a topic, a surface understanding, before following the citations to dig deeper and fully validate the summary.