You know, when you click on someone’s profile and you see they have 3 followers, 274 total posts, and 17 "thanks"?

EDIT Also, if someone thanks you, how do you know who it was? I'm not getting any notifications when someone does, and the only way to tell appears to be to go through all the posts I've ever done and see if they've been thanked

The arrow on the bottom left corner of a post. 

Quote from Halfastbracegirdle >>

The arrow on the bottom left corner of a post. 

 Thanks!

Note that on a phone the arrow/thank button only shows up in landscape mode

Quote from Noksa >>

Note that on a phone the arrow/thank button only shows up in landscape mode

 Thanks. I hardly ever look at the forums in landscape so I never knew it was there. And almost all of my viewing of this forum is on my phone 

You can also see it by toggling "Desktop View" in your browser menu.

But how do you thank someone you don't know, and doesn't have any post's? 

A d&d moderator was very nice to me and helped me with a problem i had, but i don't know how to thank a moderator i don't know.

Quote from Skyisk >>

But how do you thank someone you don't know, and doesn't have any post's? 

A d&d moderator was very nice to me and helped me with a problem i had, but i don't know how to thank a moderator i don't know.

 You don't. You thank a post (or rather, you like it which is translated to thanks on your profile), and the aggregate number of likes your posts have attracted are shown on your profile.

If a moderator did something to help you, just DM them. Nobody gets paid based on them, so it's not a big deal. It's a meta tool anyway and mods probably get tons of likes so it wouldn't even register to them really as a mod. A DM better communicates your feeling.

Or just leave it. Respond to their communications (DM, forum post, however they communicated with you) with appreciative post, and leave it at that. They would probably appreciate that more than new DMs.

Ah thank you, much appreciated.

Quote from Noksa >>

Note that on a phone the arrow/thank button only shows up in landscape mode

 Oh!!