The failsafe is at least an "are you sure" prompt. There may also be admin approval required, I do not recall the precise details.
And yeah, the squares are present on every profile display, not just the gallery - they are visible in the main profile and, on large screens, on the user portion of each post. And they pretty much designate seniority, longer-standing members have more squares than relative newbies. The girl and teen section have special colors, as does staff.