Either make it possible to delete them, like Emma said, or only make an automated wall post the first time a legendary/epic card is drawn and not every time you get a duplicate. Especially on mobile, where you can only see 100 posts (regularly if you do not switch to desktop mode) I've had many occasions where I was only able to see like 3 or 4 'normal' posts, because of all the chocolate frog card posts. 

I took care of it. / Ich hab mich drum gekümmert. :)

I do agree with you...but to be honest, I have the feeling that a lot of the people grading have not even read the rules regarding grading (taking points away for assignments being too short, too uncreative, etc.) So I do not know if this would work that well. When I grade I find it unfair to give someone who put no effort into their work an O, but a person that wrote so much, really thinking about it and putting everything in an assignment, but e.g forget their sources get an EE. The whole grading system should have a small update - maybe even a little test (exam like) that people have to take before starting to grade, just so it is made sure, they know the rules of grading.
Apart from that I think your idea is very interesting, but having higher standarts should maybe give you higher rewards. It would still be unfair, to give someone who put WAY more effort into their work, only half of the housepoints - just because they want it to be graded with an advanced grading system.
This is something, probably not as simple as you think - at least I think so.

I agree, but just so you know: posting posts in topics (like RPGs) will get you exp points, but no housepoints, while grading and writing homework will give you both exp and housepoints. So people that are doing a lot of RPing will have more exp, and a higher level, than people that grade a lot of homework, who will have way more housepoints.

I have the same problem on my mobile phone and Laptop. This does not occur on my computer I am usually on.

Oh yes! I am excited! I just hope that you cannot simply buy the once you like...maybe get them as a level up reward or be able to buy a chocolate frog + card in the shop (where you do not know which card you get) - I'm looking forward to it!