Yup. Simple Ceaser cypher. Used as a functional equivalent of the [spoiler] tag in text-only media, and to obfuscate names of people/organisations/things you want to post defamatory rants about, so they don't come up on search engines.
Certain newsgroups use it excessively for comic effect, as a sort of swear filter for terms they find offensive. So as we might talk of the "p*nct*r* fairy", denizens of ye shedde might say "have to ohl an arj one", or monks of the scary devil monastery might talk about supporting Hohagh[1] Linux. The net effect of this is that you end up learning them as words in their own right, as it's less jbex than reaching for the ROT13 button to decode them...
[1] The official Linux Distribution of the Klingon Empire.