Has squatting gotten worse on Namecoin? Squatting is fairly hard to handle in decentralized naming systems in general. Namecoin got a lot of squatting issues mostly because of the pricing function (price of names dropped over x years, and now it's almost free to register names). Here is another paper from WEIS'15 that studied squatting in Namecoin: http://randomwalker.info/publications/namespaces.pdf

Isn't that true of normal domains, too?

Depends on the toplevel suffix. For instance, .fr (France) domains have a "no taking" period after the expiration date, where nobody can take it from their previous owners. The owner can then take it back, but it won't be re-activated for a couple of weeks, I believe. So the punishment for screwing up is a temporary blackout of your domain name.

.com, .net, .org domains are handled differently, and may be easier to lose permanently.