First: No need to be rude, "in situ" is a very commonly used phrase among English speakers, as should be evident from the Wikipedia article [1] you yourself cited
Second: The normal Firefox translate feature replaces the text in the page with the translated text - retaining its styling, position, context w/ images, etc. The right click menu, does not. I described the right click menu as "not in situ" which is correct.
Second: The normal Firefox translate feature replaces the text in the page with the translated text - retaining its styling, position, context w/ images, etc. The right click menu, does not. I described the right click menu as "not in situ" which is correct.
[1] https://en.wikipedia.org/wiki/In_situ