Specifically on LW we have an (unwritten?) norm that if you post a link, you should also provide a summary using your own words. Which probably was designed to counter this strategy.

It is not specific to LW, but a custom of good practice that personally, I have followed ever since there has been such a thing as a link (and before then, when the equivalent was posting to an email list a cut-and-paste of someone else's words without any words from the person posting). I also practice the custom of ignoring links that come to me without context.

I recommend both parts of this practice to everyone.