Hi Alexey !
Indeed they are not deleted but marked as invalid, but the result is the same: it's not possible to get invalided points back after optimization.
Even if the optimization is not reversible, it would be good to be able to get the invalided points back after optimization, so that it would be possible to re-optimize and get something almost identical than an "Undo" button.
Duplicate chunk is sometimes time-consuming while working with huge chunk, and because of filtering/optimize is a recursive duo to converge on an accurate result, it would nearly need to duplicate the chunk each time we apply some filters in order not to do a double-undo (or even more) on the recursive process.
Regards