Basically, I tend to assume most folks are smart enough to figure this stuff out without me to lay it out for them. "You're an old person who is tottery on your feet? And you're grateful to a stranger for giving up their seat on the bus? Sheesh, you shouldn't have got on that crowded bus in the first place. You should have stood there and waited for the next bus. Or taken a cab. I'm only saying this because I'm concerned you could have got hurt. I care about you. And you're clearly too dim to figure any of this out for yourself, which is why I need to say it."
I may be overestimating the intelligence of our fellow Disboarders, but I hope not.
(For what it's worth, I grew up Quaker. "I have a concern..." is frequently our special version of, "Bless your heart" or "What a gem!")