Personally, I like the idea of keeping some of the practical heritage of any clothing detail. Thus I only really like handkerchiefs that could actually be used for something in an emergency, i.e. cotton or linen. Silk seems completely impractical for a handkerchief, while it actually makes some sense for a tie. To me, it would be like wearing satin silk gloves. I don't disagree that a silk handkerchief can look good, but it's not for me. I also don't like the term 'pocket square'; it is one of the most ridiculous terms I can think of and reflects the idea that the item is for decoration only (which in many cases it is). However, in some sense all clothes are for decoration only, so why not call pants 'leg rectangles', socks 'foot tubes' and ties 'neck strips'. It's probably just me. But say it to yourself a few times.. "pocket square.. pocket square.."