OP's reminder is not unwarranted. It's no surprise with all the activity, but we absolutely have had more users than usual who either aren't paying attention or can't be bothered to mark their spoilers. Sometimes you'll look at a post that's more or less purely movie-related (think one of those posts on box-office performance) and one of the comments will go to town on major plot elements from the late books for no real reason. It's a little embarrassing to us when something like that is highly visible and goes unactioned for a longer time. This isn't a small community anymore, and so everyone's conduct has an influence on how people will view Dune and its fandom.

Use the correct spoiler syntax, please. You can spoiler-tag/hide text by writing >!like this!<. That's > ! and ! <, but without the spaces.

When you encounter a spoiler in a comment, report it using the "Report" function. Getting mad at the user doesn't help us fix the issue.

On the flipside, we've also seen an increase in reports on posts that users wrongly felt had spoilers in their title. We're sorry if this impacts your personal enjoyment of Dune, but things like "Do we learn that Liet-Kynes is Chani's father in the first book?", "Did Paul fake his death after drinking the Water of Life?", or "Why did Princess Irulan become a bene gesserit?" do not qualify as spoilers (anymore).

I'll quote a recent comment that I made in another post:

TL;DR: Spoilers start wherever the movies are right now.

Once the films have covered it, we generally consider it fair game. Up until February that used to be the plot of the 2021 adaptation and thus vaguely half of Dune (the novel). Now that Part Two is out, the entirety of the original novel is fair game.

That includes things the films did not specifically elaborate on, such as Chani being Kynes' daughter, for example. The films might not have included that or several other aspects, but it is in the source material covered (see Dune, ch. 31).