Question

why can't we post links?
we usually need to show diagrams and stuff!

Answer 1

Because there’s no telling what else kids would choose to post!!

Answer 2

The webmaster doesn't want disruptive people to make inappropriate post/diagrams/etc. But here is what you can do to post your "diagrams and stuff".
add a space between the first h and the next t and that, together with the rest of the url, will post.