I play by myself a lot too. I don't think a single should be pushing a foursome. According to the USGA section on etiquette "a single has no standing on the course" I try to lay back and get some practice in with putting and chipping. I'm wondering if anybody's pet peeve might be singles running up behind them ticked off and wanting to play through.
I thought the bolded portion was considered antiquated or had been updated? I thought I read this in another thread.