I used character styles that set the proofing language with hot keys assigned, so shift-alt-1 sets to English, shift-alt-2 to German, etc. As character styles they apply both to the current insertion point when typing or any selected range (e.g. when I forgot to set it proactively and now have a line spattered with wiggles)

Or just set the proofing language for the entire text to None to banish all spelling and grammar diagnostics.

Yes, I have the same problem. Some programs handle this better than others. The Affinity suite is esp. bad.

That's not a problem with the squiggles as a user interface, but with the software assuming that you speak only one language.

At least in Firefox I can select multiple dictionaries. Firefox will ignore words that are a match in any of those languages, at the cost ofc, of typos that are in one language but not another so sometimes I'll right click and uncheck a language temporarily.

On most systems I use I've managed to set it up so that I get spell checking in all languages I use. So I only get a red line if it's not a valid word in any of the languages, which is pretty useful.

While your point is valid, I think you are missing the point of the article.

The point was that someone the author was fond of passed away. The author who likely might be reading these comments. And Krueger did some cool stuff that everyone use without realizing who did it.

Oh yeah - typical American thinking behind it. Everybody knows English and only uses one language.