Dude Apparently You Are Old If You Still Do This

Apparently nothing says your old, than if you do something like this.  Can you Identify what it is?  If you've been reading this blog you should have been able to identify it by now.

Apparently if you're under 35 you don't do this. I'm over 35 so this definitely looks weird to me. I can tell you that it's a very hard habit to break. Can you see what it is yet? You should have picked up on it by now, but if you haven't, keep reading.

The two paragraphs are very different and in case you can't see the difference, in paragraph one, all the sentences are double spaced after the period. In the second paragraph the sentences are separated with only one space.
When did this happen? I didn't get a memo, and I remember getting a letter grade taken off in high school if I didn't double space after a period.  I talked with my kids in high school and college and they all single space.  WTH?

What about you?  What do you do?  Tell us in the comment section and tell us your age...be honest