I wonder about the possible bad consequences of the spacewalk to remove the gap filler material. If the spacewalker yanks too hard, is there a chance that some tiles will come loose, making the problem much worse? And if he yanks too hard and the gap filler stays put, how sturdy is he mounted to the station's arm? Is there a chance he'll pull himself on to the tiles, or even the arm itself could hit the tiles? I don't know how much slop or play is in the robotic arm.
In terms of the risk management used for making safety decisions during flight- in the past, before Columbia, they measured the damage after landing and then declared how safe they were. Now, with all of the extra cameras and inspections, are they going too far in fixing little things that don't really need to be fixed? Did they run some computational or hypersonic wind tunnel tests to see if this gap filler will really cause a hazardous situation? I know from personal experience that this can be very complicated and take some time to set up to do correctly. Maybe they got this data before the mission? Or is there enough of an unknown impact that the risk of causing additional damage is worth removing the uncertainty?
I'm afraid that for every future mission, the routine dings and pings on the tiles will cause much consternation and maybe unnecessary repair work. Will this work take too much time from the main mission tasks? It will be interesting to see how the re entry adds to the now-documented dings and pings on the orbiter's underside.