The only time i’ve ever encountered any sort of problem is at trail centres with long singletrack climbs (eg. Afan) where you’ll catch a slow rider (or group of) who seem hell bent on keeping your behind them. Second to that is catching up with a stopped group who youve been hauling in, who when they see you coming desperately set off ahead of you when by far the most sensible option for all would be to let the quicker group through and continue shooting the breeze with your mates for another few seconds (which again we do if we are caught).
By contrast to mrlebowski I’m not sure I’ve ever had this sort of experience, and I live in the Afan Valley and so ride there all the time. This does give me the option to avoid ‘rush hour’ a lot of the time, but I do ride a fair bit of weekend daytime as well. Mind you my technique for getting by people has been described as ‘politely aggressive’, which is a back-handed compliment if ever there was one 😉
I find ‘Could I get past, if/when you have the chance’ a good phrase. Makes it clear that a bit of cooperation would be nice, but I’m not expecting anyone to dive off the trail out of my way.