Hi Bluefish,
Just some additional points.
From my experience those adjustable columns are intended to be temporary, although we see them frequently left in place. The real question boils down to their installation and their purpose.
Properly installed they would have been inspected with approved footing below and similar approved support above. Thus at some point the house could be supported, the temp columns removed, and a permanent concrete filled metal pipe installed, or other approved support. I don't think this is the case.
As for their purpose, are they holding up the house or just stabilizing some beams to reduce sagging? If they are just stabilizing old sagging beams (not broken failed ones) then they are not structural and if removed or they failed the house would not fall down, just go back to sagging as was probably the reason for them in the first place.
So, if the question arises from a potential buyer, suggest they are not structural and just keeping the floors level. If desired at any time the new owners can have them replaced but they in no way compromise the support of the house. That assumes no broken beams are being supported.
Bud