It appears to be an outside link to a PNG, but I do NOT click on outside links...
Sounds like he wants to learn your IP, which I think others have been banned for PMing similar.
Not at all, it was just a plain PNG delivered from the University server. The reason to post it as a link was that the bitcointalk image proxiy often truncates PNGs for no obvious reason, and it did so in the preview. I have re-delivered the Lesson without the link.
(If sending links in private messages is forbidden, why does the software allow it?)
There was a rash of people sending beacons a year or so ago, and links to sniff IP addresses. If I recall some were banned. You'd have to ask a mod why the software allows it.