AI Spam

[razvan]

But if you look closely at the quoted text there will be a link hidden in there. I can't imagine how hiding a link where nobody is likely to ever see it is worth all that trouble.

It's not intended for human eyes to read it but for the search engines. Since its early days, one of the main variables used by Google to rank a web page was the number of incoming links to it from elsewhere ("many web sites link to this page, therefore it must be useful and I will show up higher in the results"). It's a very common technique with blog spam as well. Most if not everything is typically automated and done at a large scale, so the effort is minimal.

The wikipedia entry on comment spam (https://en.wikipedia.org/wiki/Forum_spam) is a starting point for more info and countermeasures.