Sorry for the delay in replying, I was away last week. I'd be happy to help where I can. I'm not sure I'd have time to be able to test the idea but I could certainly give feedback if you thought it might help.
Really nice idea. I love ideas exploring both the human side of tech enhanced learning, and ways of adapting learning to the individual.
Just thought I'd pop a few of my initial thoughts down. I work in developing learning systems for higher education and I've been caught out before by things like this, so I thought I'd mention them just in case. They may or may not be of use.
I agree that your trickiest challenge will probably be tuning the algorithms just right. Determining matches through engagement is great but also has the small risk of a filter bubble developing. Students may be inclined to engage more with content that conforms to some extent to their pre-existing views. It's also useful to be clear on how you define 'engagement'.
Have you thought about moderation of the pins? For example, would it be up to viewers of pins to report anything that may be offensive? Who might determine if such a pin is offensive or not?
From a technical point of view (algorithms aside) I don't think developing the platform would be too bad. We have developed something similar (but without algorithms) to help design students curate and critique work collaboratively. Students have found this sort of 'pinning' and sharing activity engaging and effective. The likes of Pinterest, Instagram and Facebook have set some informal design/process standards that we know work. Building on these gives a great foundation.
Depending on how diverse you want your user-base to be have you considered a low data/offline lightweight version for those users who might not have access to reliable, fast internet and decent hardware? In a similar vein, in terms of diversity are you thinking about those with disabilities? If so it's worth making sure you consider accessibility from the start. And language - would people be matched by language, or would you include a translation capability?
Anyway, just a few thoughts. Really enjoyed reading your concept. Some exciting ideas in there. Good luck!
I think it's really useful to add a physical element to online learning. It's something we do at the Open University for various courses e.g. within the technology and design areas. I think there's scope to explore concepts around this further. Not just to aid learning, but to help with community aspects, and also just to blur the line between online and 'real life'. I think where someone has spent money on an online course, receiving something tangible helps give a greater initial feeling of value.