I'm wondering if certain common capture cards are known to "clip" whites or "crush" blacks if they are above or below a certain level? Seems like there are lots of posts identifying those faults after the fact in different capture samples.

My understanding is that some capture cards will still capture content outside of legal ranges, but I assume even those have limits on the high end in particular.

If a capture card has ideal automatic gain control, it would linearly scale down the entire waveform to get the brightest level to 100IRE so as to compress the dynamic range, but not to clip or crush high or low levels.