Apparently, this is a new(?) New Reddit feature, links like https://www.reddit.com/topics/a-1/ go to a page listing topics starting with "A". It would be a perfectly rational assumption that www.reddit.com/topics/ should also go there; however, Reddit is irrational, and you should not under any circumstances visit that URL at work or in polite company. (It redirects to a rather NSFW post with the ID "topics", presumably for ancient legacy reasons.)

Reddit should probably explicitly redirect the parent URL to the topics feature, so more people are not surprised by this. And maybe make sure there's a policy in place to properly reserve such URLs in future features.

This was discovered, by mistake, in the Reddit Mods discord, and according to the comments, Peter made the same mistake a month ago; so, for Peter's sake, you ought to fix this.