I can't count how many times this has happened to me. Trace an issue down to some piece of code that makes it look very intentional, then have to go spelunking

I can't count how many times this has happened to me. Trace an issue down to some piece of code that makes it look very intentional, then have to go spelunking through whatever history I can find to figure out what the actual correct specified behavior is. Bonus fun when you have to start reaching out to clients to find out if anyone is relying on it acting that way.