I have read the three answers you brought as concerns ice skating on Shabbat. I have also shared these answers with colleagues and with friends. You commented that the groove is not sufficient for planting a seed. Nonetheless, does this qualify as p’sik reisha d’la nicha ley, and thus would be forbidden d’Rabbanan? Is the fact that the groove in the ice is k’lachar yad also relevant? Thank you.
Psik reisha refers to a melacha which is accomplished by a person who has no intention for the melacha, but it is nevertheless a necessary result of his action. For instance, dragging a heavy bench across a yard produces a furrow that if produced intentionally would be a melacha. In the case of ice skating there is no sufficient groove, there for no melacha, therefor no psik reisha. I repeat, I do not think ice skating for sport is a suitable Shabbat activity, but in some climates it may be a reasonable way to walk to shul.