OK, I think I understand your complaint now. When you use the discourse search function, it takes you only to an individual post, but not to the search term within that post. I agree that for long posts that is inconvenient, as you then need to scroll through the post and look for the search term, which is not even highlighted.
Ctrl-f-f helps in some cases, but doesn’t really solve the problem - for long topics, it will only return a subset of the “hits” for that term. To revise your example, say you go to https://forum.inaturalist.org/t/how-to-use-inaturalists-search-urls-wiki-part-2-2/18792, but instead of searching for “term_id” (which occurs only in the first post in the topic), instead search for “habitat”. Using the default (ctrl-f) behavior of the Discourse search bar, you will find that the term occurs twice in post #1 and three times in post #24:
In contrast, if you use ctrl-f-f, you will usually see only the first two occurrences (in post #1) because post #24 is not yet loaded in the browser. To find those other occurrences, you would need to scroll down the topic until post #24 loads, and use ctrl-f-f again.
I hope this explains a bit why Discourse uses this non-intuitive search default – they assume that users want to search within the entire topic, not just in whatever portion of the topic is currently visible to the browser-based search. There is certainly room for improvement, but that would be a topic for the Discourse forum, not iNaturalist.