Bence Damokos wrote:
On Mon, May 24, 2010 at 6:17 PM, Guillaume Paumier
This was reported on http://commons.wikimedia.org/wiki/Commons:Usability_issues_and_ideas/Archive_1 The reason offered to explain this issue was: http://www.facebook.com/help/?page=416 → Bugs and known problems → I don’t have a preview for my link. I haven't investigated in details, but it may be fixable on our end.
Commons pages are indeed missing those three recommended meta tags, but I am not entirely sure that providing them would solve the problem (it's worth a try though).
Thanks, Bence
That doesn't explain why other commons pages show a preview.