This topic of discussion has also just happened in one of my vivariums. I have just witnessed what I believe is the same scenario with my two. I have two beardies that have been together since birth and I am convinced they are both female. I have had them for 12 months now and also have two other deffo male beardies in other vivs. I have studied internet pages for information and guidance on all things beardie over the last 18 months or so and my personal visualisation of the vents suggest two female. I do admit that the vent situation on one is difficult to assess because there is little/no obvious bumps or pertrusions, but I believe this usually indicates female. Aswell as that, having two definate males in other vivs means i have witnessed a males behavior with headbobbing and deep black beards many times and the way they behave. I have had the two males reacting as you would expect when this suspect male/female beardie is within site, and she/he reacts with the waving and ever so slight head bob and deffo not how two males react. I have never witnessed a black beard or major head bobbing from this suspect beardie so I am still convined it is female even tho i find it totally hard to believe that the clinch/mating session could happen between two females. I shall keep you informed of further developments, but I am still fairly confident that they are both females as the original poster on this topic believes with his.
Scott
Scott