What is the difference between and in HTML, and do they affect website rankings?

Answer 1

I would use them the way they are semantically defined: DEL for text that has been removed, and S for text that is now inaccurate but hasn't been removed.

These may mostly appear the same, but could be handled differently by screen readers and other accessibility tools - DEL may be ignored completely (eg: not read out) and S may be read out but differentiated from normal text.