I usually put a "non-breaking space" before the mdash. Otherwise, you might get something that looks a bit like this:

There are some good people on Hive
— such as dbooster and enginewitty.

But with a "non-breaking space" ( ) before the mdash code ( —), the mdash will never appear at the beginning of a line after a line-break:

There are some good people on Hive —
such as dbooster and enginewitty.

I love the mdash and the ndash, too. I also wrote about them in my blog maybe seven years ago. So, "Kudos!" to you for doing the same! 😃