I suppose, yes. The library is turning drug infested and into a sex den. The comma is replacing all the words “and into a.” Which is essentially what you wrote. I guess i was trying to point out they were two separate situations and that drug infested is not describing the sex den. I was also trying to establish that commas can replace words and phrases. Although the example I gave above only replaced one word, it would make sense they would replace other words, as well, to shorten the headline.

I guess there are actual headline specific grammatical rules that are followed. While not a comprehensive list, some of these rules include leaving out auxiliary and some joining verbs, articles, conjunctions, etc, and replacing some words with various punctuation. Apparently, the list goes on.