This is probably more than you want but:

One fix is to use "styles" to define your bullet settings then you don't have to worry about indenting and/or backspacing to remove indents. Matter of fact, using "styles" for the complete document would be recommended:

Understanding Styles in Microsoft Word
Tips for Understanding Styles in Word | ShaunaKelly.com


Why use Microsoft Word’s built-in heading styles? | ShaunaKelly.com

Sometimes, learning the tricks of the trade can be for the better...Hope this helps.

I do like that better than just switching to shift + tab, since I've been meaning to get into styles for some time.

But I still feel like it must be possible to just toggle this setting. I can't believe that computers would become so inefficient as to not have an off-on button for a setting that, based on the view counts in the topics I linked to, thousands of users have come to rely upon.

Granted. And it may be that that is what I have to do, and it may be that I would be better off for doing so. But I would at least like to confirm that before I proceed, if not for me than for the sake of posterity.

If it's true that there is no way to turn this setting back on, I at least want to be told as much.

Understood. I have not come across this particular issue (probably because I use styles exclusively) so I do not have an immediate solution but, I will continue to research the issue. Hopefully, another user may be able to help you out before then.

//UPDATE// I just went back and reviewed your referenced links from your initial post and found the posts within those links to be a few years old. With the latest comments of those responding to those post being from MSWord MVPs (subject matter experts...IMO) and indicating the use of the backspace key being unreliable in MSWord, I would be inclined to believe that as gospel. Therefore, I would suggest the use of styles as mentioned in my above post.

Thank you, and thank you for all your help with this.

It is checked as "on". But I have tried switching it to "off", and then back "on" again. Neither worked.

Yes, I saw that too, and I was worried that that might mean there was no way to toggle the setting back on. But the MVPs' responses were vague as to whether it was impossible to turn the setting back on or just not worth it (because the setting would tend to become shut off again erratically), which is why I came here to look for further assistance.

Since users seem to have this problem very frequently, I thought it might be good to try to settle the question definitively with some more recent responses (since, as you said, some of those posts are quite old), so that when future users go searching for a fix they will see once and for all that there is none.

It's unfortunate, but it's still good to know rather than to waste time looking for a solution that does not exist.

Again, thank you for your help with this.