I got a problem commenting on wpmu.org

I tried commenting on this thread via Facebook: https://premium.wpmudev.org/blog/manage-multiple-wordpress-sites-from-one-location-with-this-free-tool/ and after clicking "comment" a few seconds later I am back on that page and my comment is nowhere to be seen.

Could someone please check that out?

And just for completeness, here is the comment I was trying to publish, maybe someone can help over here:

I wanted to give infinitewp a try but on the prerequisites site I get this warning:

PHP should be able to access files in the same server through a full url

And I got no useful reply on their forum or via email. Its a self managed server and all I need to know is what is missing, a php setting or module?