If on a new page those new comments would get downvoted to oblivion. If on an older page they'd be partially identifiable by dint of being on an older page.
But sure, things could be done to make this more difficult. It's probably not worthwhile on Reddit's part to do anything to stop this, just as it hasn't been too worthwhile for websites to evade ad blockers. The number of people who mass delete is just too small to matter.
If I worked at Reddit and wanted to do something about it though (and was a programmer), I'd add an option under individual deleted comments for viewers to click to view the comment (and any versions). And possibly add an option for viewers to restore a version entirely. This would save helpful comments, at least until some jerk decided to automate the process and restore everything. So maybe the complete restoration is a bad idea.