[redditmigrant]

The title should be "StackOverflow now has a dark mode" instead of "StackOverflow has now a dark mode".

[airstrike]

No, it really should be "Introducing Dark Mode (beta) for Stack Overflow"

[frosted-flakes]

Also, Stack Overflow is two words.

[lopis]

Both are grammatically correct. "has now" gives emphasis to "now" while "now has" emphasizes "has".

[scpedicini]

While adverbs can come after an action verb (in this case, 'has' functions as an act of a possession), as a native English speaker and a former ESL instructor I have NEVER heard the phrase "has now" or any similar phrases such as, "he has finally a car". They both sound extremely awkward.

[ravoori]

Interesting, what is the difference?

[saagarjha]

"has now" is ungrammatical.

[frandroid]

The former uses the right word order.