They are not no-no’s for me, but then, I have taken classes in dreaming and have a regular dream practice and group, and I am curious and open about what may be going on with dreams, and have had many interesting experiences with them and have heard from others about others.
I think the negative reactions tend to be balking because the person posting tends to write “what does it mean if I had dream X?” and questions which are written in ways that seem to have different premises and assumptions than the audience make one feel obliged to mention those differences rather than answer implying that for example, if anyone has dream X, it means Y.
Also we have many skeptics and physical materialists and people who just don’t think dreams mean anything and feel like that opinion should be noted on nearly every such dream question.
In the classes I have taken, there is a very helpful and important practice taught about how to answer this type of question, and that is to word the answer so that it avoids implying that you know the meaning of the other person’s dream because, as @Darth_Algar very correctly pointed out, the real person to interpret a dream for someone, is the dreamer himself. Nonetheless, having someone else listen and respond to one’s dream can be very useful if framed carefully, because we very strongly tend to respond to our own dreams in limited and habitual ways, and simply hearing how other people take them can have us approach them in all sorts of new ways, which can be remarkably effective at getting us to see things about them and about the issues our subconscious conjured them for in the first place.
So what we generally make sure to do is start out an answer by saying something such as, “If that were my dream, I would think that maybe….” instead of “I think it means Z” because that implies you think it means Z to them – it’s a subtle shift, but it removes one layer of translation that the listener’s brain needs to make in relating to what you’re saying.