You may have changed how line ending markers are handled. I've never seen an editor treat a Windows line ending (CR+LF) as a double line break (Unix is LF and Mac is CR), but I suppose it's possible. You can see the opposite effect in the default Windows Notepad when you open a file with Unix or Mac line endings; it won't show any line breaks at all.
I use
Notepad2. It's small (618 KB executable) and fast, and not overburdened with a bunch of features that most people will never use or even know exist. The only downside is that it doesn't include syntax highlighting for Lua, but I find syntax highlighting annoying anyway, so I don't mind the lack.
