As a past customer of Gandi, they have been bought out and have been significantly increasing their prices (renewal this year would have cost me twice what I paid a couple years back) while reducing the value proposition of their offering (e-mail is no longer included…)

Note that while entering the Schengen area does not require a visa for USA citizens, you do have to get a visa waiver which is subject to limitations. See this document.

If you don’t want to spend the time, you could have simply critiqued the image for being hard to read and interpret, as you are doing now - and requested they provide the source of the image (or the data). That would have been perfectly valid - as this image has seemingly gone through a lot of jpeg-ification and screeshotting, making captions and labels hard to read.

While not understanding French is understandable, Google Translate and other tools can help with that nowadays. You ought to be careful when levying critique on a post, and ensure it is valid. Your mistake was noticed by me in this case, but this could very well be the misinformation against which you caution.

Regarding the laziness in sourcing: I agree that sourcing is not properly provided here. A reverse image search surfaces that many of the plots are available here and refers to the source also stated on the image (Apur), which seems to be an entity with regularly does analyses regarding mobility in Paris, which has analysed these topics before. Whether you trust this source is still up to you, but the source is not simply an anonymous person on the internet.

Reading the annotations on each of the plots, these are all average NOx concentrations of the labelled year, not point measurements - as you are insinuating. Furthermore, the color scales match up too. (edit) Do note: the more recent plot is zoomed in though and scales are much less clear!

I think it is fair to say that recent policy changes, like rejecting private vehicles from the center and promoting active transportation work. Though aftereffects of COVID (work-from-home) may be a contributor too.

Neat idea. This could be refined by adding a git hook that runs (rip)grep on the entire codebase and fails if anything is found upon commit may accomplish a similar result and stop the code from being committed entirely. Requires a bit more setup work on de developers end, though.