There are several tools for viewing them, primarily based on Pushshift, an apparently individual-run database that grabs whatever it can from the Reddit API, usually within a few minutes. The frontends come and go; currently the major ones are unddit.com and reveddit.com (which honours user deletions, refusing to show them).

There are also Pushshift-based sitewide search engines: redditsearch.io is made by the Pushshift creator but doesn't show deleted content. ihsoyct.github.io does, but is unreliable, often randomly missing some comments and posts in any one run of a query.

With the amount of constructive comments/posts removed for seemingly no reason nowadays, and the blight of users overwriting and/or deleting helpful, otherwise anonymous comments when making privacy purges, I find it now more pleasant to browse with all deleted content shown than without.

Offer up something more than a vague "I saw this thing one time, trust me on this"?