If you’re more likely to edify someone, leave them on. Otherwise, wash them off. They’re meant for mutual reminder, not for letting everyone who is not fasting know that we fast.
We’re supposed to let the world know we belong to the Lord by our love, not by the ashes.
Well yeah, letting others who don’t fast know that we are fasting on Ash Wednesday is not a terribly important thing to do. But, in addition to the more important reminder that all things end that and that we should consider what happens next that is not limited to Catholics, I think it is worth letting people know that there are those who fast
at all and pay attention to religion
at all. It’s not a matter of saying “we’re fasting, you’re not, why aren’t you/we’re better than you.” It’s simply a physical visual reminder that there are things beyond the mundane (and that contemplation of such things is not a purely private matter to be hidden away), as well as a reminder that we should take our views of greater reality should effect how we behave in more places than at home and at Church.
Yeah, our love is the most important thing to show, but this does not mean we should discount the value of physical signs. There’s a reason that we place importance on relics, though they have no inate powers, why we build statues, even though our minds are very capable of thinking of a person without staring at inaccurate likeness that probably looked nothing like them, why we have crosses, etc etc. We are animals as well as spirits and physical signs affect us. Yeah, ashes aren’t that big a deal. But they can be a small deal, and the fact that they are not as important as other things does not mean they cannot be put to good use.
In much the same way that one of the least important parts of being a priest is wearing that collar everywhere, and yet every time I see one it reminds me of all that the priest stands for and of the fact that there are still people who stand for it. Ashes are pretty small potatoes in comparison, of course, but even small potatoes are nice every now and then.
Basically, all I’m saying is that the edification need not be limited to other Catholics remembering that they need to get a fish sandwich today.