System:limit has a quirk that's bugged me for some time, which I'v not posted about previously, because it seemed like too much of a special-case solution, but I now realize that special case may not be so special after all.
The basic issue is that when you set a "default" system:limit under options, it's not a default at all, but a maximum. You can include an explicit limit in a search, but only one smaller than that setting in options. But typical use (at least for me?) is wanting to keep result sets small for quick responsiveness, and then increase the limit once I've narrowed things down sufficiently. As is, that means going to change the setting in options, refreshing that search, then putting the setting back where it was.
Of course the solution is to make it so the explicit presence of any number of copies of the predicate throws out the default entirely.
It occurs to me that I'd actually love similar behavior for other predicates as well. Specifically ratings, where only the not-worst things are desirable under normal circumstances, but you occasionally want to scrape the bottom of the barrel.
So I propose that rather than having a single special option for the system:limit, there be a place under options where we can set a default set of arbitrary predicates, which are individually discarded in favor of the same predicates on the same targets being explicitly mentioned in a search.
It should be noted that this would also function as a soft alternative to the blacklist, allowing specific tags to be excluded by default, but still shown when explicitly targeted in a search.