Firstly, thankyou for being constructive, considerate, & solution-focused about this. Unfortunately a lot of other mappers are not, and just dismiss the problem.

“There are two conflicting guidelines here: the one you refer to, and the universal principle that changesets must be consistent (e.g. if you need to revert them).”

I'm unsure of the guideline to which you refer. Would you cite the relevant documentation, please.
I ask not because I doubt the claim, but that I simply want to read more.

“It is unfortunate that Jersey is included in any bounding box that includes, say, Saint-Malo and Carentan. Do you imagine the number of changesets that would require to avoid that, for a single change in the French rail network?”

I sympathise.

While more sets would be needed, I don't see that it would have to be many. A central France-only set, then a wide-short one (landscape orientation) to cover St. Malo, Brest, etc. A portrait one to cover the Thumb of France peninsula (since it shouldn't matter about extending out into the sea; perhaps except for those mapping seamarks).

I'm amused by the thought that this would all be so much simpler if the Channel Islands were still French territory.

There are open bug reports re tools handling large bboxes in less simplistic ways. I gather that it's a difficult problem to overcome (perhaps because of all the extra processing it would require).

“We have started to discuss solutions such as including #France in large changesets, so as to facilitate automated filtering in your monitoring tools. Would that be an agreeable way forward to you?”

I greatly appreciate this effort.

Something like tagging the changesets with such a clear hashtag would, I think, work elegantly under the circumstances.

For context; I do surveying via a nano-computer, thus use OSMCha for filtering. Though, if I recall, it handles hashtags. I'll need to check if it's able to apply a negative filter on them, though. For some things it can't; only an inclusive filter (editor string is one parameter which has this problem).
However, even if it can't, yet, then a real-world application makes for a stronger case to have the feature added. Plus, other filtering tools will still benefit.

So long as it's consistent, and applied when all the changes are only within France, then yes; simple, graceful, easy (to implement at both ends), and sounds like it would be effective.

I'm inspired to do some tinkering with OSMCha this afternoon.

Nor will it be completely solved with tools (at least one developer has stated that there's currently no workable solution for this commonly suggested remedy).

There are open tickets re OSMCha.

Until magic is implemented, then the only mitigation is to keep changeset bbox small (as is best practice anyway).

One of the problems with filtering out large bboxes is that it also excludes the ones which do make local changes.

Ultimately, more granular filtering requires more processing (by a third-party).

Not really any different to claiming that the solution to spam is better filtering; that only addresses the symptom, not the cause.

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Hint: north-west corner of your bounding box.

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

osm.wiki/Changeset#Geographical_size_of_changesets

What makes for osm.wiki/Good_changeset_comments

Looks like you added several building outlines.

If it were only covering a single county, I probably wouldn't be aware of it. But it spans multiple.

My request, besides being good practise, is because many large changesets appear in the local list for my area (which has few contributors). There are more jumbo changesets (that make 0 local changes) than there are local ones.

Sure you can.

Why do you feel that you can't?

That might have been true 1000 years ago, but the Channel Islands are no longer French territory. So, since your bounding box includes them, the changeset doesn't comply.

That's how I became aware of it, in the first place.

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Source?

Further evidence: a call for Broad Street to be reopened to motor traffic http://petitions.gov.je/petitions/200485

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets

Smaller changeset areas, please: osm.wiki/Changeset#Geographical_size_of_changesets