Lee Carré (2021-09-29 17:41:50+00:00): “the vast variety of sources tags I've seen that are often inaccurate or unclear and the fact that I only made those changes in SC from afar, that I am absolutly certain about, I still think, that in this particular case it doesn't matter”

Wouldn't they make exactly the same argument?

See Moen's Law of Littering: http://linuxmafia.com/~rick/lexicon.html#moenslaw-littering
“People tend to litter where there's already litter.”

Instead, take pride in setting a good example.

Otherwise, well, if none of it matters then why bother at all? Especially if that makes work for others to clean up.

“changes should of course be verifiable by others and the acccurate source tag might help with that.”

Only vandals believe their changes to be inaccurate.
How's anyone else supposed to evaluate the changes of another mapper?

Recent example (I'll even cite the changeset if you like); an account which seems to be of a government employed removed the name=* of a government building. There was no source=* and the comment didn't even mention said removal (let alone why). This all being the account's first changeset. This doesn't inspire confidence. It may have been an unintentional change (which I've seen happen, before).

Citing source=* WILL help. It helps other mappers.

If I, as a surveyor, encounter something which doesn't match reality, and was contributed by an armchair, then I have no qualms about correcting it.
If, however, I saw source=survey, then I'd be more cautious. I'd check more info, and maybe even ask the previous mapper first.

Another (real) example was being unable to find a retailer for which there was a PoI node. No source=*, no contact:*, last-modified years ago.
So, I had no idea what the addition was based on. Maybe it was wrongly tagged (and they meant something else, nearby, for which there might now be a duplicate element). Maybe it really was there, but has since gone. I have no way to judge; only guess. So, I either have to leave it be and wait for an answer from a mapper who stopped contributing years ago (and so may never answer) meanwhile leaving possibly inaccurate data on the map, else I have to change / remove something which I can't find (but may simply have missed; for example I add fire hydrants and more than once had great difficulty locating the plate with relevant metrics, sometimes concluding that it must be missing (and stating so in a note:fire_hydrant), only to then find it after I submit the changes(!))

Other cases have involved info which isn't apparent during survey, but maybe the other mapper got it from a non-survey source which they didn't specify. Should I remove that which I can't verify (yet might be useful), or leave it be (which risks leaving inaccurate / outdated info on the map)?

So, source=* is vitally important, for a whole bunch of reasons.

At the very least, include a note(:*)=* (as a tag), or a comment on the changeset, to indicate the situation, reduce ambiguity, and help future mappers to decide if they can confidently apply their changes or not.

Another reason for setting source=* accurately; I recently discovered that a local mapper had been copying from a source which wasn't obviously public-domain and didn't grant a license (thus is proprietary by default), yet hadn't been specifying source=* at all. This makes all (similar) changesets lacking source=* suspicious, especially given the minefield that is draconian copyright and its trolls.

Same with the government newbie, earlier; why shouldn't I regard the change as a mistake, since I have no reason to think it genuine? Seems that it should be reverted. It's not on me to do his verification work for him (by going there to survey the site).

This, of course, is all on top of how much of a pain in the arse it is to even check the edit history while out surveying. To then discover that some armchair jockey simply couldn't be bothered citing their source.

Another way of characterising the difference (between survey & local knowledge): let's imagine, for a moment, that the relevant resources were unlimited and posed no practical problems with what I'm about to describe. Imagine source=survey as being changes which include photos of what the mapper saw (in order to verify), versus ‘local knowledge’ being far more casual from memory.
Human memory is dubious, yet photos are rather more objective.

The only difference between that, and current practise, is that surveyors are trusted to be truthful and acting in good faith (and if not, then other local contributors would dispute questionable changes, based on their own familiarity (local knowledge)).
Someone claiming their changes are from their memory, rather than inputting the data while on-site, is less reliable. Hence survey is regarded as the highest standard.

If an armchair does well, then it's a whole lot easier for a surveyor to indicate confirmation of accuracy (and spend a lot less time determining what's what). Those cases are a pleasure to survey; I can do a lot more of them per hour than when it's all orphan tags.

Another issue is position: it's often undeclared. It doesn't match GNSS / survey. Sometimes it might match some imagery (which is badly aligned, to start with). You see the problem, I hope.

“In my defense, I wasn’t aware of the tag set by SC”

SC is intended & designed for users to not need to know the clockwork.

However, it has clear warnings against editing anything which hasn't been surveyed. SC is intended for surveying (hence the nature of the questions it asks). These would've had to an dismissed and/or ignored.
Compare: in my defense, Officer, I didn't know that driving through a no-entry would cause a collision. I very much doubt that the cop is gonna be impressed that you ignored the sign saying to not drive along the road in that direction.
Instead of assuming it'll be fine and ignoring it, a better way would be to ask why it's there. If for good reasons then you learn, if for outdated or bad reasons then it may prompt change to improve the situation for everyone (maybe you've found a bug).

You could've seen what it was uploading by examining your own changeset history after uploading quest-answers. There are links to wiki articles about common keys & tag values, to learn more about them.

“In the end I want to help make the map better and more accurate for everyone and not cause additional issues.”

Then diligence. Think of it as a way to convince others to not revert your changes. Imagine editing a wiki without citing any sources to support your changes.

Like with good comments; eventually the other mapper you'll be helping is your future self.

Quality over quantity.