"I wrote this under duress" is my favourite comment I've personally left, mostly so the poor bastard who maintains that code after me doesn't hate me quite as much.
It's still not a good practice. Customers do sometimes see log files and when they do it's because things are broken and they're typically not in a good mood.
Perhaps you have a highly orthodox individual as a user, should they be forced to read or even repeat a 'God Damnit' in a log or error message while on the phone with support? Should an atomic-bomb survivor be told that their files were nuked?
I probably wouldn't either. It's not that I wouldn't like to write those things, or enjoy reading them in the tribulations of those who'd been there before me. The problem is more when it reaches a customer via some error prompt which you modified for debugging or some logging output which ends up in their console.
I wouldn't make it at a company that frowns upon a 'God Damnit' in a log message.