This is EXACTLY my question, too. The front part of the PCI-e x 16 slot appears identical to the adjacent PCI-e x 1 slot. I am using internal on-board graphics, so I don't need a graphics card. I do, however, need another PCI-e x1 card. The BIOS setup in this motherboard has a setting to "FORCE PCI-E TO X1", so I don't see a problem. But I have failed to foresee problems before.
I'm not particularly interested in being the 11tht person to blow up an nice MATX motherboard and a PCI-e x1 tuner card just to test this theory. It is not an SLI board.
I would think that somebody more brave, foolhardy, and/or knowledgeable might have settled this by now. I did find a PCI-e x1 adapter cable that terminated in a long connector suitable for PCI-e video cards, so perhaps the PCI-e x 1 slot contains enough data capability to operate a graphics card, but undoubtedly not at full speed.
There are others in this forum who say that there should be no problem putting a x1 card in a x16 slot, so I'll give it a try. Any more words of encouragement?