I think we can all agree that what peds/cyclists ahead need to be told is "Hold your freakin' line!" and/or "Single file on a two-way MUP!" But (1) it's too much for some people to comprehend, and (2) it seems rude to say it even without the expletive.

So we say something that at least has a chance of communicating to them which side we intend to pass on. I get that a lot of people can't understand it, but I don't know how else to communicate it. To someone who's walking down the middle of a lane (and I don't mean just MUPs, there are as many wrong-way runners and walkers as there are wrong-way cyclists in my area), a bell or horn doesn't even have a chance of telling them which side they're about to be passed on.

The bottom line is that no matter how important the workout or the rider we're trying to impress, unless you know that the person you're passing has acknowledged you and knows which side you're passing on, you just have to slow down to barely above the speed of the person being passed, and give them the same three feet we demand for ourselves, even if it's on a MUP and it means going into the dirt, even if it means stopping behind them and waiting until traffic clears in the next lane. Yep, it's a PITA. Especially when there's lots of traffic. But anything else is dangerous.