The "pardon the interruption" modal is the only one that I have ever seen.
And it's not immediate, there's time enough for your eyes to adjust to the content of interest before that modal pops up. It's as if it's designed for maximum obtrusiveness.
The experience is further degraded by a header and footer that not only take up significant screen real estate but also only seem to exist to also prompt me to sign up.
So that's three obtrusive prompts asking me to sign up - the modal, the header and the footer. This is unique in that the annoyance has a depth of redundancy.
Try old.reddit.com - it was originally created for users who want to revert to the old desktop layout but it has an additional, unintended feature: even on mobile, it maintains the desktop layout without switching to the mobile site (note: it is not responsive so you will have to zoom - but personally I prefer zooming compared to the nagware "features" of the mobile site).
And it's not immediate, there's time enough for your eyes to adjust to the content of interest before that modal pops up. It's as if it's designed for maximum obtrusiveness.
The experience is further degraded by a header and footer that not only take up significant screen real estate but also only seem to exist to also prompt me to sign up.
So that's three obtrusive prompts asking me to sign up - the modal, the header and the footer. This is unique in that the annoyance has a depth of redundancy.