Today I learned hyphenated words are largly obsolete

"Printed writing is very much design-led these days in adverts and Web sites, and people feel that hyphens mess up the look of a nice bit of typography," he said. "The hyphen is seen as messy looking and old-fashioned."

I see the dictionary editor they quoted is still fighting back.

That's a sweet ass-car

- Good ol' #37.

You mis-spelled “to-day”.

there are times when punctuation is actually useful for clarification!

And capitals for readability.
- yeah, without them capitalizing that first t their comment is completely unreadable
- hyphens are dead, capitalization is next.
They can rip “E-mail” from my dusty old hands!

I like to use them when words create a unit of thought. Like line-of-sight, and such. It really helps readability. It prevents people from having to think too hard about certain sentences when it's ambiguous which words belong to what part of the sentence. Especially when the expression contains function words like "of".

However, I'm a fan of just making multiple words into compound words, like bumblebee. That doesn't work well with something like lineofsight, though.

As a side note, I wish we would bring back the diaeresis in favor of hyphens in words like co-op. It used to be coöp, and that is so much more fun. Or words like reëlect. Even when it's not abbreviated, the diaeresis makes it more obvious to readers how coöperative is pronounced. Or any other time where two vowels in a row are pronounced separately.

Albeit always confuses me. Albeït is so much better.
- Sobeit
I think you would be more convincing if you spelled "line of sight" correctly
- Good catch. I fixed it.

they are a bit old-fashioned

I'm gonna argue with the title.

Obsolete means no longer of use, in a general sense.

Just because people don't know that the tool is there, or don't know how to apply it, doesn't mean it's obsolete. Hyphenation still has its original utility, it helps communicate in writing what is evident in speech.

I get what they mean, but the title is not accurate to the rest of the article, imo.

Take a second to actually read this one. It's pretty short and sweet. It's also from 2007, and talks about nouns (maybe compound nouns) that we really don't think and probably never knew were hyphenated. It's not about the use we typically see today.

As an aside, I've noticed people start hyphenating in weird ways, like "I've been at this job for 7-years"

I think at this point MS Word automatically recommends a hyphen after any number + quantifier combo. One time it wanted me to correct "three armed guards" to "three-armed guards" which would have changed the meaning considerably.
The number of times MS autocorrect suggests incorrect changes to grammar is laughably high, and most people just blindly follow the suggestions.
- I fucking hate autocorrect. I mean to say "its" a lot more often than I mean to say "it's", but Gboard on my phone tries to change it to the latter almost every time.
  I say "almost" because it did it the first time in the above sentence, but not the second time, so it managed to make the wrong guess for both of them. Goddamn useless trash -- Markov can suck it!
- Three-armed guards would probably be in very high demand, depending how functional the extra arm was
Could the strange hyphenation be due to the influence of their mother tongue? I don't know if there is any language that does it like that, but it seems plausible.

A question from a non-native speaker: Is there a definitve guide on American punctuation somewhere? I always wonder about American use of punctuation inside single quotes when quoting a term instead of a sentence, and some other cases where I see different intepretations of punctuation.

There are different ones for different kinds of writing (general, academic, journalism, and more). Chicago Manual of Style is one of the general ones. It's good, and considered authoritative, but you have to buy a copy or an online subscription.
A free one that I like is Purdue OWL (Online Writing Lab from a university). It's easy to understand and has good info.
I found this. It seems pretty good. Although I don't really think it matters much. You'll likely be understood the same.
- Thanks. I think it is quite well made, and I would love authors read this before they hand in their manuscripts...

is old fashioned non-hyphenated?

like red tree

My experience is more "feels" than fact I suppose, but I've always seen it that any adjective or noun playing adverb to another adjective or participle should be hyphenated to the word it describes.
Red-hot coals (coals that are hot to the point of being red)
Red hot coals (coals that are both hot and red)
Ruby-red shoes (shoes that are as red as rubies)
Ruby red shoes (ruby shoes that are red)
Smooth-talking rogue (a rogue who talks smoothly)
Smooth talking rogue (a smooth rogue who talks)
Bamboo-eating panda (a panda who eats bamboo)
Bamboo eating panda (bamboo is eating a panda)
- ruby shoes that are red
  You mostly nailed it but this one would be “red ruby shoes”
  determiner, quantity, opinion, size, physical quality, shape, age, colour, origin, material, type, and purpose

You should use replace the - with space or nothing at random

icecream ice cream ice-cream

Nah, just turn the first word into an adjective.
"Iced cream" sounds far more sophisticated than boring ice cream.
- Hmm, marshed mellow ...
- Or add - to words that don-t need-it
  Iced-cream

*To-day

You think we (Americans) are smart enough for that?

Adjectives get a hyphen because it clarifies their position in the sentence. I'm a proofreader and I will absolutely fix it if you leave it out.