Yeah - I see that now. Looks like it was uploaded 2010 with a GEDCOM file which has since then been deleted. Original Profile Mgr no longer around. No reasonable way to go back and find what the original character really was, although it does appear that it was intended to represent a copyright character. The black diamond with the white question mark is intended to represent a "replacement character". So Jonathan is 100% correct - the black diamond/question mark is not the problem, just the symptom, unless that object itself causes profile bios to become invisible.
Jonathan, as a test, can you add the "replacement character" to another profile and have someone who does not have rights take a look and see if they notice anything different? (or you may have already done so). If it turns out that the character causing the issue is that one (which I'm beginning to lean that way), then it should be a simple process to just write a script to look at bios and remove that character anywhere it shows up. Minor impact overall, but it could open up bio information that should have been available before.
As far as the symbol goes, from what I can tell, it's a Tahoma font, last symbol on the chart - called a Replacement Character (reproducable as U+FFFD for those of you who understand recreating such a thing).