"New interaction modes" are different ways of using the features of SE to accomplish different things.

Just like using the edit history to assist in knowing only the new content. It makes perfect sense now that you've suggested it, but I probably wouldn't have thought of it on my own, at least not quickly.

Similarly, in the Meta.SE post I linked to (meta.stackexchange.com/questions/262297/…), it never occurred to me that the search functions might be that robust. In general, I've actually been very dissatisfied with the usefulness of SE search, so I pretty much have ignored it.

This all is part of a broader dissatisfaction with the SE model, in that new users are faced with a large, complex system with poorly defined rules.

There are high-level guidelines, sure, but the subtleties are sufficiently numerous and complex that there are periodic occurrences of posting something, doing something, encountering something, whatever... that gets a response from someone better versed with the system with a whiff of "gah, why didn't you KNOW this already?"

The biggest example was my first encounter with 'review audits': meta.superuser.com/questions/9347/…

I had no idea that such a thing even existed, and then all of a sudden when I was trying to figure out why the site seemed to be misbehaving when I was trying to review a post, I got chastized for failing the audit.

(Chastized by an automated message, even.)

It all reminds me of when people tried to get me to play Mao as a kid. The point of the game seemed more to harass new players, than to actually play the game itself.

SE has sufficient "point" that I've stuck with it... but all of this has cast something of a negative hue across the experience.