I think the concern is in the way it obscures the target. Replace "Moby Dick" with a Chuck Tingle (warning, probably nsfw) book. Now that second link is a serious problem.
I see what you're saying, but it doesn't seem like much more than a funny gag you might pull on a friend.
If a website is concerned about that case, then instead of letting it inform their URL design, they should have a "Warning: Adult content. [Continue] [Back]" interstitial like Reddit or Steam.
I'm not even sure it's a serious problem - a possible annoyance, and perhaps, for a spammy site owner, maybe even a feature. But as a web user, I'm not really fond of that added uncertainty.
If a website is concerned about that case, then instead of letting it inform their URL design, they should have a "Warning: Adult content. [Continue] [Back]" interstitial like Reddit or Steam.