I'm using Squarespace to create a fairly straightforward site for a restaurant. Squarespace uses their flavour of markdown syntax when creating menu items, and for the most part it's pretty fool-proof. I did hit a small hiccup, however, when I needed to add a dollar sign ($) to a description for a menu item.
The problem is that when Squarespace sees the dollar sign, it assumes that text is for the price, and moves it to the bottom (which messes up everything else).
Here's the incorrect markdown:
Loch Duart Scottish Salmon Salad
Grilled sustainable salmon served a top of mixed spring greens, tomatoes and cucumber, with your choice of dressing (substitute with sesame crusted seared tuna steak for an additional $3)