I often see questions on Stack Exchange sites which I presume are written by non-native English speakers who use the word "doubt" in place of the word "question". Is this a case of misunderstanding the correct meaning or are people being taught that this is correct usage?
This is Indian English. See Vishy's Indian English Dictionary.
July 12, 2006
Vishy's Indian English Dictionary: doubt
doubt. /DOWT/. A question asking for clarification. In standard English and American, the noun doubt is uncountable and refers to a lack of complete trust in something. Doubt may be expressed as simply as doubting someone's abilities or as profoundly as someone doubting their own religious faith. Not so in India. In India, doubt can be used as a countable noun. When a school teacher goes over an intricate concept in class, she invariably leaves some students with doubts in their mind about their understanding of the material just covered. Students ask her questions to get a better understanding of the concept and each such question is called a doubt. It is entirely normal to hear a statement like "I have just one doubt, miss" or "If you have any doubts before the exam tomorrow, come see me in the staff room". The doubts in the aforementioned sentences are not as much rooted in a lack of faith as in a lack of understanding. Attentive readers would have encountered the Indian English sense of doubt a fair bit on online message boards in threads started by Indians. Titles such as "Visual Basic .NET/Oracle doubt" are not uncommon for threads on programming-related message boards. It is my understanding that this sense is mostly prevalent in southern India, but I could be wrong on this count.
A native English speaker does not recognize "doubt" as a synonym for "question". The examples given (like "Doubt about TinyMCE content css"), no matter how prevalent, are awkward. Even if it can be justified by picking a fitting definition entry, it's not something we would ever say. We understand it, but we also understand when a French person says "Let me explain you something".
Saying "question" instead of "doubt" is a better choice.
In most cases when this happens the person is really a non-native English speaker as you said.
In some languages that grew from Latin the word that is used for doubt can also be used for question. Dúvida is the Portuguese for doubt, but it can also be used as question. For example, when kids at school say to the teacher Eu tenho uma dúvida (which word-by-word would translate as "I have a doubt"), they mean that they want to ask a question to the teacher about what has been taught. And if I go to a store in Brazil and say Eu tenho uma dúvida sobre esse produto ("I have a doubt about this product" in word-by-word translation), what I mean is that I want to make a question about the product.
The same happens with duda, which is the Spanish word for doubt. It may also be the case in other languages, but I'm not sure.
Therefore, when you give a presentation and native Portuguese speakers say "I have doubts about what you said", don't think that they don't quite believe in what you said. They may just have questions to ask you.
I'm not a language expert, but I've been dealing with a lot of those doubts…
By opening with "I have a doubt", you don't simply state "I have a question; …" followed by question's content, but instead you claim that "I understand all this, but …" before bringing to discussion a particularly unclear aspect of the topic. The construct as such is therefore not good or bad, nor is it in any way rooted in Latin as suggested above (my native language is of Latin origin and we don't/can't abuse the "doubt" either in original or in translations, while the Indians do it without having the Latin heritage). It is all about the correct usage in a given context.
The expectation when using this construct is that what follows the "I have a doubt", either the question itself or the whole conversation about it, should show that indeed you have gone to the process of analysing the problem at hand on your own, and you are stuck in a detail for which you need clarification. However, you will find that many of those asking have no idea about the big picture either and haven't tried to solve the problem on their own, and this is why you tend to answer them "No dude, you don't have a doubt, you simply have no clue about this subject". It is in such context that the use of "doubt" stands out and annoys in the conversation.
Now whether this is a vocabulary issue (unlikely) or it can be explained in the Indian context by a tendency to 'fake' knowledge by using "doubt" to make the question asked appear as a minor clarification request, that I leave to others to sort out.