Thank You = Has at least 20 liked posts
Appreciated = Has received at least 1 like on 20 posts
But thatās the same!
Thank You = Has at least liked 20 posts
would be something different. ā¦ or not? 
What I read is:
Thank You you get when you liked 20 posts writen by somebody else.
Appreciated you get when at least on every 20 posts you have writen you have received 1 like.
Since the next step from āThank youā is āGives Back: Has at least 100 liked posts and a very high like ratioā Iād say this badge too is talking about likes you received on your posts.
So Iād say they are the same, but there may be a minor difference in the coding which isnāt translated in the badge description which causes one person to have the appreciated badge but not the thank you badge. (Would be interesting to know who this person is - but I donāt have to go through them all right now).
I interpreted it as different statistical values, where:
Thank you - you have at least 20 posts i which you received a like
Appreciated - on the total amount of posts you have a mean of a like in 20 posts
So for example if I have 40 posts in which I received 2 likes I should have the Appreciated badge but not the Thank You one because I have only 2 total likes
I hope to be clear 
but I donāt know if itās right 
Other forums, which use the Discourse platform, have wondered about the same thing:
Apparently they already made changes to the description (which will come to the Fairphone Forum in a future update of the forum software):
2 Likes
The update is here 