How important are human-readable slug components in a social platform's urls?

I'm working on a new social platform and we were discussing our url structure. I've noticed that sites like HN, youtube, facebook, and vine use only some type of encoded url fragment and that's it.

e.g. https://vine.co/v/e0mQeEep1IJ

Whereas reddit and others use an encoded fragment AND an optional human-readable component.

e.g. https://www.reddit.com/r/funny/comments/3oc22e/this_guys_facial_hair_makes_it_look_like_he_has_a/

Is it safe to use only the encoded fragment and not include the human-readable part? The only reason we considered the human-readable part is for SEO purposes but is that even important at this point?

Any info appreciated thanks!