Getting Started: Copy Pasting the code causes severe error

I’ve been going through the getting started guide and when I reached at the end I try to copy paste the comment controller from guide and I got into situation from which I got out after 2 hours. I’ve tried to add comment but I got 500 from my server.
After many hit and trials I found there are some hidden characters got pasted when copying the code from website after re-writing the code 500 error got fixed.

I think this issue should be fixed.