1) WDW officially does not go along with saving chairs.
2) If you remove towels, etc to take over the chair, no problem.
3) The other folks might (probably, will) complain when they come back.
4) But, the CM's will back you, not them.
NOTE: This is just like trying to save places for parades. The CM's will
back you up of you take someone's "saved" place.