HATE it

The only time it's remotely acceptable is when there's an outright sequel series. Scanlating the original and sequel in parallel is sometimes okay because the sequel series is designed in the first place to be amenable to new readers. It's generally a rebranding with the explicit purpose of attracting a new audience.

Even then I prefer for them to catch up on the original first. Still waiting on Daiya no A 😛

Trolls don't make money on trolling.
That doesn't make it okay.
Publishing a scanlation of a random chapter in the middle of a manga doesn't, in any way, contribute anything, and only serves to annoy/anger people
...so, in essence, it is just trolling.

As I'm firmly opposed to both the reading of a sequel before what came before it, as well as making the sequel amenable to new readers (this also often applies to later books in a book series. For proper readers, who read in order, it only makes things needlessly more clunky and awkward, at the start), I don't consider that scenario to be acceptable/okay
...though I imagine I may be in the minority, in having that opinion.

Well, there's been only one time I've been totally okay with this: in Tokyo ghoul, when due to popular demand an awesome fight scene has been scanlated first, skipping ten to twenty chapters. Raws were available, too.
But otherwise I've never been fond of skipping. I ignore it, because people have their reasons, so it's "oh well"

No no no, it is unacceptable, I can't accept, it's so bad. I HATE IT

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MILESTONES
1st: Death Note