Not every pen on the desk has to be a loaner

[maywrites]

I don't think refusing to lend a fountain pen is automatically unkind. Someone who isn't used to one may press too hard or hold it at an awkward angle, and the pen is still yours to look after. I'd rather offer an ordinary ballpoint for a quick note than treat every pen I own as communal.

[morganp]

If someone just wants to see what a fountain pen feels like, I could let them try a couple of strokes on scrap paper while I keep hold of it. That's different from handing it over to use on their own.

[nibcurious]

That works as a quick nib demo, but with you holding the pen they can't tell much about how it feels in their own grip. It's a sample of the line and flow, not a full tryout.

[pencilshavings]

Fair point: holding it only shows the line, not the grip. A basic fountain pen kept for people to try themselves seems better than passing round whichever pen happens to be on the desk.