How to Properly Obfuscate Sensitive Information when Asking for Help

I use IRC a lot for talking about and getting/giving support for FOSS.

The Problem

Every once in a while people are asked to paste logs, configs, output, … and some people feel a need to obfuscate certain information like IP(-Range)s, domain names, usernames, … but all too often fail at that for some reason from the point of view of the one giving support.

Possible Fails

Inconsistency:
Fail: Replacing a certain bit of information differently in different places or missing occurences
Example: bob@example.com becomes foo@example.org in one place, foo@example.com in another, and stays bob@example.com in a third


https://tools.ietf.org/html/rfc2606
https://tools.ietf.org/html/rfc5737