Can I also just point out that "I was exhausted." is not passive voice! And "Our work here is done." also shouldn't be highlighted, it's absolutely fine. What the hell? With these kinds of false positives, this seems like it would do more harm than good.
Grammatically the passive voice uses the equative verb to be with a past participle of the verb. Both those phrases satisfy that condition.
Semantically, the passive voice involves action being done to the subject. Both those phrases also meet that condition. Rearrange them and you'l see:
[1] "I was exhuasted" --> "${SUBJECT} exhausted me". The phrase may not seem passive because you've elided the subject, which is part of the problem of the passive voice, it lacks clarity
[2] "Our work here is done" --> "We completed our work" Like the first phrase, this phrase elides the subject of this sentence, the individuals doing the work. In this case, including the subject ("We") may feel repetitive because of the pronoun "our", but its still more precise.
Also, passive voice isn't bad, however it most often lacks clarity. Sometimes that's okay, and sometimes you want some flexibility with your sentences for effect, such as ending a sentence with the subject (one of the primary reasons to use the passive voice).
I don't think that a correct analysis of the sentence. The exhausted is an adjective, similar to I am tired, but saying "Something tired me" would have a totally different meaning, because it's a different, unrelated sentence. ("I am covered in green paint." also doesn't seem like it's passive voice, but maybe I'm wrong.) As far as I can tell, "our work here is done" is indeed passive voice, but it is also perfectly fine English, and thus must not be highlighted.
"I was exhausted" absolutely does not "lack clarity". What could it possibly be unclear about?
Looking at http://www.lel.ed.ac.uk/~gpullum/passive_loathing.pdf, I'm also suspicious of your definition of passive (p.7):
> ...passives do not always contain be and do not always contain a past participle. They also do not always obscure the role or responsibility of the doer. They may or may not have a subject (the passive clause in any monument defaced by vandals does not), and they may or may not have a by-phrase (The president has been assassinated does not). Sometimes they specify the agent of an action very clearly (as in It was thrown at them by hooligans), and sometimes not (as in It was thrown at them); sometimes they specify the undergoer (as in A surfer was attacked by a shark) and sometimes not (as in Being attacked by a shark is no fun). Often (as in (3)) there is no action whatsoever, rendering the strange phrase “receives the action” inappropriate.
I'll try to add some clarity to what I said (because passive voice isn't the only way to muddy the linguistic waters).
A passive voice doesn't make the sentence bad and often the passive voice does constitute perfectly fine English. When saying, "I was exhuasted" I may have no idea what drained me of my energy, in which case a passive is totally appropriate. However, it does lack clarity for the very reason you suggest "${SUBJECT} exhausted me" changes the meaning--"I was exhausted" doesn't specify who or what is responsible for the action of the verb. By not mentioning what exhausted you, the sentence looses a small amount of specificity.
"I am covered in green paint" is also passive because what covered you in paint? Something or someone is doing the paint covering, but by using the passive voice you can obscure the subject.
While we are recommending articles, Orwell has some enjoyable things to say about the use of the passive language in politics.
https://www.mtholyoke.edu/acad/intrel/orwell46.htm
Writing in such a way so that you can be understood isn't sufficient. You should always write in such a way so that you cannot be misunderstood, and using the active voice with its higher specificity goes along way towards that. However, exceptions will abound. As one of my professors used to say, "Language is the result habits--all of them bad".
"Our work is difficult."
> The term ‘adjectival passive’ is often applied (perhaps not very felicitously) to active clauses with predicative adjective phrases in which the adjective derives from the past participle of a verb and has a passive-like meaning. There is frequently an ambiguity between be passives and adjectival ones. For example, The door was locked is ambiguous: as a be passive it says that at a particular time someone took the action of locking the door, and as an adjectival passive it says that during some past time period the door was in its locked state. Since the complement in this kind of clause is an adjective phrase, verbs other than be can be used (The door seemed locked, as far as I could tell), and so can adjectives derived with the negative prefix un- (The island was uninhabited by humans).
Grammatically, the passive voice also places the active participant as an explicit indirect object rather than the subject. A sentence without an explicit indirect object is not in the passive voice.
It may still have some of the same problems of communication which motivate people to work to avoid the use of the passive voice, and may even go further than the actual passive voice in those problems in that rather than deemphasizing the actual actor -- as happens when that moves from subject to object -- it omits the active party entirely. But its still not in the passive voice, despite the similarity in issues that arise.
This is not true. Something as simple as "I was sat on" illustrates this well—in English, the subject is still required but the actor is not. This is much MORE so for eg Latin, where verbs take voices with much less context.
"I was exhausted" is ambiguous, using either the imperfect passive voice or the imperfect "to be" with a past participle. However, it's perfectly valid to note as passive as it is, in fact, passive under one of the two interpretations.
This is not correct. It happens to be true if the verb is transitive and denotes a physical action, but that is accidental. The passive is defined in syntactic terms (including the past participle you mention), not in semantic terms.
“He was diagnosed with flu” is passive voice, and appropriate, because the diagnoser is not important. We care more about the flu than the doctor.
“Mistakes were made” is evasive and serves to obscure, and should be avoided.
It might even be worth pointing out that the "authoritative basis" for all of this passive prohibition is an unfortunate misreading of Strunk & White. The Elements of Style merely points out some cringeworthy ways to misuse the passive, and suggests that it shouldn't be your go-to voice.