No, it is definitely not the projector. Here is a trusted review at http://www.hometheaterhifi.com/projectors/projectors-reviews/benq-w1070-projector/all-pages.html that stated:
"When using the HDMI input, color and tint controls are disabled, so unless you have calibration equipment, all that you will be configuring on the BenQ are the brightness, contrast, and sharpness controls. Setting those is much easier when Whiter-than-White and Blacker-than-Black are visible, but those are clipped by default. They can be made visible by setting the HDMI Mode to PC from Auto, which I would recommend doing.
I'd also recommend sending all your content in the YCbCr 4:4:4 colorspace. Using 4:2:2, the BenQ used lower quality filtering on chroma detail, and the timing was misaligned by half a pixel. Using RGB produced similar results, but 4:4:4 was handled properly and should be used if possible."
I saw a couple of other reviews remarking about the clipping but I am sure they were not aware to change the settings. I am using an Oppo player and there is no clipping. Switching between PC and Video settings and comparing the image is meaningless without calibrating, the Brightness and Contrast settings will need to be set at different values to produce a similar appearance for the different modes. I don't understand why you said you are "pretty sure" that you were still getting clipping, if you are using a calibration disc, clipping levels above 235 will be obvious because you will not see the bars from 235 to 255 no matter how much you adjust Contrast.
Is your projector connected directly to the player? An AV receiver can also limit the range of signals passed through it.
I am feeding the projector directly from a Panasonic DMP-BDT210 Bluray player. I checked tonight, inputting PC Signal still clips, in order to not clip I have to output RGB also. Others on this forum suggest the same is true with Oppo players, and also that the Panny doesn't clip with other projectors.
I just switched to YCbCr 4:4:4 output from my PC and I noticed an immediate improvement, it looks sharper now maybe? Not sure why, but it's definitely better for real.
Thanks (I'm always surprised by the things I learn here, even after over a year of owning this PJ, it still impresses me).