引用自 quietvertigo：

Can I safely return to Iox and Myari without setting it off?

Yes, once (IDK if more) as long as you don't willingly break it or leave the moon while it's covered with an item you placed
This should be all you need to know to recognise an avoid it when the time comes.

I think ptor above is slightly wrong. And I don't think there's reason for spoiler tags, since this is very vague. The correct answer is: Do not break or cover a thing you find on a late moon. If you do cover it and then remove the cover you can still go back but you can no longer go to Iox.

引用自 pev69：

If you do cover it and then remove the cover you can still go back but you can no longer go to Iox.

IIRC I could. but it was a long time ago so I'm possibly wrong

And the possibility that it also is based on prior actions is not to be forgotten, so it even could be you still can get to Iox, i'm on my third itteration, and there are quite some changes in the narrative now...

And i think spoiler tags are to be used more than nessecary, some people are not pleased with learnig to much too soon.
thats why my misses likes teh universal hint system, if she can't grasp the inteded operation.

引用自 quietvertigo：

I'm wondering what the point of no return is, spoiler free if possible, tagged if not. I'm trying to explore as much as I can without ending the story before I'm ready. Can I safely return to Iox and Myari without setting it off?

Six will prevent your return to Iox if you continue to chat about what direction the main hopper points to. (the one you later block off).

Exactly.

(not sure how much of a necro this is as I can't see the year posted) Is there a way to continue forward without ever blocking off Iox? edit: Ok, it looks like this point is the true main point of no return.

I unfortunately blocked off Iox early this first run, oops.

You can finish the game visiting all moons and not blocking off Iox. In fact, blocking it off gives a rather rare achievement.

Rare? I accidentially got it on my first playthrough.

I got it on my first one too. But according to Steam, only 3.8% of players have this achievement. That's the 2nd rarest. The next one is 7%, which incidentally I couldn't do even though I tried.

And number 1 rare meat is unlocking it again ?

Would not wonder me if there is a possibility, if one answeres a conversation with Six like a Nerd instead of a know it allmost :-)
On Elbereth you can abble a bit at the back of the Bar, about the patois, i ended it with stating a knew a bit, but it would not wonder if one gets further with an answer Six knows more about :-)

With some other knowledge is presume an avid Sailor cab hopper around the Uni-Verse, getting unseen onto Iox