Yes, sending messages to other users would be a great feature.

Very interesting would also be a search function to find old own posts (or also seek posts from other users according to different criteria, for example key words).

Talking about old posts: unfortunately I noticed that in some of my posts (especially in articles older than two years) quite some images are not shown anymore. In one of my recent posts I named some examples of old articles with missing images. What is the reason for that? Did it happen during migration process to another database?

And yes, to honor your efforts: I like the "Coin Marketplace"! :)