I don't know what you're talking about, honestly. On a generated image that's suspected of being NSFW, there's a drop-down that lets you choose how long you want to allow NSFW images to show. Then you click Ok or whatever. And it shows the image.
I don't know of any "invisible" filter, that's removed after you generate a ton of NSFW images.
Click the button and it shows the usual dropdown. Change that, and tick the box that you're 18. Then click the button to save. The image then immediately shows up.
I apologize for the confusion; I did a bit of investigation and here’s the clarification:
The filter I mentioned is located in the "Public Gallery," not in the generated batch shown to users. It operates as follows: after you generate NSFW content and choose to display your own NSFW (by turning off the filter in the dropdown located on pictures), and then go browsing "Public Gallery" with [none] filter applied, there will be no NSFW content visible in the "Public" gallery unless you generate NSFW content around 10 times. The NSFW content will not be displayed immediately; it's true that the batch you generated will be shown as you mentioned, but the public gallery won't.
This hidden rule only applies to the "Public Gallery." If you visit any image generation for the first time and check a known NSFW gallery name, the NSFW content will appear without any further restrictions. You don’t even need to click "generate" at all.
Okay... I have been using perchance for like 6 months or so, looked at many different generators, and have never seen this happen. So, I don't know how I've managed to dodge that all this time, but you get it every single time. Very unusual...
I get this behavior as well... but for me it is on my "personal" gallery that i made with a long convoluted name to prevent anybody form using the same name... so basically just another form of this "public gallery" you talk about. any image in here marked as NSFW will always be blurred, no matter how many time i tick the box to undo this. Maybe a browser issue? i am on "Edge".