Every single time you see a post or comment that threatens someone, harasses someone, or incites violence, use this link to make a report that will almost certainly be ignored until they really pile up.

Simultaneously e-mail a report to contact@reddit.com.

Don't spam them. There are plenty of examples; spamming is unnecessary.

Here's a screenshot of where the contact links are found. Follow those instructions:

http://i.imgur.com/nkDXDdo.png