In English Who did lock this door? is a little marked, if you're not being emphatic. In general, the simple past tense with -ed (or the irregular equivalent) is accepted on this course, and not the form with did. There's a little discussion about the difference here: https://english.stackexchange.com/questions/118683/difference-between-did-verb-and-just-verbed
"I didn't lock this door, but it's locked. Who did lock this door?"
In Klingon I might express it with lojmItvam ngaQmoHpu' 'Iv'e'? or lojmItvam ngaQbejpu' 'Iv? Adding the did puts one of those kinds of emphases on the English.
[It also feels perfective to me, as you can see from my back translation, but that's another discussion, and I'll leave what to accept here to the course creators.]
The most reasonable interpretation is certainly perfective. (There was an incident of door-locking, and you're asking who performed it.)
The only way this would make sense without perfective is if you're asking something like whose job it was to lock the door every night. (Whenever it was time to close the store, Mary backed up the computers and John cleaned up the aisles. Who locked the door?) I daresay this is not the interpretation that springs first to most minds.
For an alternative perspective, I disagree that the perfective must be expressed here and I believe that the simple past is acceptable for this in Klingon. There is disagreement in the Klingon speaking community on this and logical arguments have been unable to bring the community together in agreement.
I didn't say perfective must be expressed here. I said talking about a particular incident that occurred is perfective, while describing a regular activity that occurred in the past is not. I also said that most people, when confronted by the sentence Who locked this door? will only think of the perfective meaning, which the given Klingon sentence does not reflect.
If an action is being described in Klingon as completed, it requires a perfective marker. If an action lacks the perfective marker, it is being described as not completed (and not continuous). To look back at an event and describe it in its entirety, or to describe its ending, is to describe it as completed.
Obviously my English teachers really did quite a number on me. So I am using°to do" whenever I see a question or a negation. In German (nowadays German) we don't use °to do" anymore. "We simply use it not." When used, it signals that your language skills are low to very very low. So it is hard for me to figure when you have to use it in English and when you don't. School drill was: negation or question: you DO use "to do"! Perhaps I overdid it;-) But the problem I see here is, that people from all over Earth, Terrans try to learn Klingon, and not all of them are of English mother/father tongue. In my language I got the meaning of the Klingon sentence pretty clear. There is no ambiguity in German. Would there be any in Portuguese, or Farsi or Hindi...? To think that a grammatically correct sentence is rejected for reasons of discussable emphasis that may or may not have been in the Klingon sentence, could make some otherwise very enthusiastic learners: sigh! But then again, it is a course for English speakers who are interested in learning Klingon, and we out there with a different language background just profit from the fact, that English native speakers, are so much interested in Klingon to create this course. So, once again, a very heartfelt thank you!! And to the others as well! Will it be possible to have this discussion in Klingon one day? Will it?
Your English teachers are correct: you use do for questions and negations.
You see a Klingon.
Do you see a Klingon?
You do not see a Klingon.
You also use it for emphasis.
*You DO see a Klingon.
Of course, Klingon doesn't have auxiliary verbs.
Ah! As a native English speaker I don't usually know all the rules, but I do (emphatic use of to do, there) know this one.
Keep using to do for negation. And if the question is formed by inversion, also use to do. I locked the door --> Did you lock the door?
But if the question is formed with a question word as the subject, don't use did. Who locked the door?
I was going to say "don't use did if the question is formed with any question word" but then I realized that I have to say "What door did you lock?" so it's only when the question word is the subject that you drop the did.
Why did you lock the door? When did you lock the door? How did you lock the door? but Who locked the door? and What locked the door?
You actually sound kind of fancy if you say "I locked not the door," because English speakers are familiar with that construction from Shakespeare. In general the grammar of low status dialects of English doesn't coincide with non-native speaker errors, and in most contexts there is not a lot of discrimination against ESL speakers, as long as they are understandable. We're grateful that you have learned our language, I guess, and almost proud that it's so hard to master. We started with Germanic grammar and then rinsed it through French and I don't know what happened.