Let's put it this way, there has been a lot of water under the bridge from over a year ago. The clearest way to deal with this is that "used to" is only used when the context allows you to conclude that the sentence refers to a repeated or habitual action in the past. It's not an expression of a state but an action (or lack of one) which says that "You were not doing anything" really is the best answer for this. Some work is being done to post some instructive Tips Notes on the Imperfect Unit. So please check back to see when that gets put up. It should make it all very clear.
I thought we had gotten through the woods on imperfect vs. Passé composé and this section was pretty well cleaned up. I guess not everybody is on board. Here is the best and most thorough explanation I have found so far on the difference between these two tenses. Have a look: https://languagecenter.cla.umn.edu/lc/FrenchSite1022/FirstVERBS.html
Should be accepted, to me.
When would you use such a sentence (in English I mean) ?
That could help us find an explanation; because as far as I'm concerned, and as a native, I understand the French "Vous ne faisiez rien" with a "to do" meaning rather than a "to make" one.
According to a given context, I'd maybe say something like "Vous ne prépariez / fabriquiez / produisiez rien" if the English was "make"...
Otherwise, and out of context, you're right though : "you were making nothing" is theoretically correct.
you did nothing = tu n'as rien fait ("tu ne fis rien", but that's very literary, not oral, colloquial French). This means at a certain, accurate point of time (or at various specific points of time) in the past, you did nothing.
you'd do nothing = you would do nothing = tu ne faisais rien. This means for a whole period of time in the past, you were doing nothing (sort of "non stop"). It refers to a habit, a condition, in the past, whereas the first example refers to a (non) action, an isolated fact.
Of course, usage and context are more relevant than strict grammar rules, which is what I just tried to explain.
I guess it is now accepted because it makes sense, the use of past simple in English / imparfait in French is not so exceptional :
The guy was on the floor, screaming, and you didn't do anything !
Le mec était à terre, en train de pleurer, et vous ne faisiez rien !
That first translation would highlight the simultaneity, the fact that while the guy was screaming on the floor,you "were not doing" anything ; yet in English I believe (as a non native who's quite familiar with English though) that the use of "were not doing" wouldn't be natural in this case.
But in French you could say the former sentence, or this one, more similar to the English:
- Le mec était à terre, en train de pleurer, et vous n'avez rien fait !
That second translation focuses more on the results, the final fact that you did not do anything.
Mind that :
"ne parle rien" makes no sense. "Saying nothing" is "ne rien dire"
FYI, all the forms you suggested are imperative; so "ne parle pas" is "Don't talk", "Ne parle jamais" is "Do not ever talk" or "Never talk", and "Ne dis rien" is "Say nothing / Don't say anything"
if you want to say those -ing forms in French (to mean the fact of not doing something), then you must say it so : "Ne pas parler" (Not talking / To not talk), "Ne jamais parler" (Never talking / To never talk) and "Ne rien dire" (Saying nothing / To say nothing)
finally, to be accurate (and it's important to understand other cases and uses), the replacement words for "pas" that you mentionned, actually need the "ne..." to mean their English equivalents. So "nothing" is in fact "ne... rien / rien...ne", "never" is "ne... jamais" and "nobody" is "ne...personne / personne... ne". The negative part is included in the word in the English version; e.g. "nobody" = "no + body" = "no person" = "ne...personne" in French
That just makes no sense in English and I can't even begin to translate it to French. Even "you used to do nothing" is incorrect here:
To quote MOD n6zs:
"used to" is only used when the context allows you to conclude that the sentence refers to a repeated or habitual action in the past. It's not an expression of a state but an action (or lack of one) which says that You were not doing anything really is the best answer for this.