I'm not sure if it's modern journalism of lazy journalism.
They aren't breaching any form of copywrite; they're citing their sources and it's more of a commentary on a thread as opposed to simply copying the thread.
It isn't just the DM.
As society moves more or less completely into the digital age, comments like "isn't there any really news" don't hold up to scrutiny as writing about a thread here or from any other source doesn't preclude writing about something else. There are no 'limited number of paper pages one which the editor can print. Isn't there also an argument that while not individually, an aggregate of online opinions can give a fair insight into the mindset or mood of a particular demographic and that is therefore worth exploring for a journalist?
I have no idea about journalistic ethics and if it would be legal but I'd feel aggrieved if they were directly posting quotes from a serious matter such as a particular case of rape or child abuse or what have you. Copying a story about a grabby bride gets a big 'meh' from me.
Suggesting it's 'outing' people is naive to say the least when those people have put the information into the public domain. You would be shocked how easily your details can be collected. My specialism is computational linguistics and an area my company has worked on is syntactical analysis of writing. I could created a database of all posts from the same user. Analyse that and compare it to other posts with a high degree of certainty all your name changes could be recorded. Assuming name changes are made after people say something that they worry could remove their anonymity, all this info could be collated. IP addresses can be collected (private messaging functions are great for (ab)using for that). It's usually possible to harvest IP addresses from people loading a page. If I were to do that I'd have a large number of addresses no doubt but comparing them with times someone posted my well tell me who they are. Searching the rest of the internet for the same user name, comparing to the statistics gained from syntactical analysis and other methods is fairly sure to tell me exactly who you are.
I could do all of that and it certainly isn't my field. If you think you have any anonymity online, you're wrong!