I might add that I've been fortunate to learn a bunch of horary astrology from "Paul," a former member here, member of Astrodienst, horary moderator at Skyscript, and just a crack horary astrologer. Although he's not here (and can't come back) to point out my errors if I misrepresent him, I will say that I asked him a number of questions about difficult charts that I attempted to read.
Paul's answer to many of my questions was that a chart should tell a story relevant to the querent's question. To me this means that despite the precision of symbols on a chart and the rules 'n' regs for reading them, at some level reading a horoscope is a subjective art. This precisely means that at some point, you may need to make a judgement call, or rely on your intuition. At some point, if the chart does not tell a story remotely relevant to the question, you might indeed "discard" (decline to answer) it.
My evidence that intuition and subjectivity are highly important comes from trying to work through the examples in the above-mentioned books, plus J. Lee Lehman, The Martial Art of Horary Astrology. In their case studies, they follow through with the actual outcomes. While I could follow the authors' objective symbol analyses up to a point, there often seemed to me to be a leap, in which their mental synapses made connections that I just could not read transparently off the chart. While this difficulty might merely reflect my own shortcomings, it also seems to me that much transpires for the experts in somehow reading between the symbols.
I think this information is confidential so I will not name several really fine astrologers with whom I have communicated who admitted to having psychic abilities. Deborah Houlding, owner of Skyscript (and author of its horary primer) was once a professional psychic.
I have no psychic abilities, but when I have been aware of a forum poster who has asked a question more than once, sometimes there was something "off" about the repeat chart. Ideally, this is what some of those cautions/considerations/strictures should be telling us.
So I think we need to be careful in assuming we know what goes on during a horary reading.
I also think that astrology gives us a rare and precious privilege to look into the soul of another human being, or of a moment in time. Although I have been flippant on occasion with people whose charts I've read, I am not proud of myself for those times, and try to do better with the next readings. Of course, we should be straight with people, and sometimes "tough love" is called for. But we dare not forget how sacred horary astrology was to Lilly and his predecessors in our craft.
Moreover, I had difficult times in my life when I had no knowledge of astrology, and when I would have so deeply appreciated an astrologer taking the time to read a chart for me without expecting I was trying to learn astrology from the process. We all start out as newbies. Most of us have painful times in our lives when we're groping for answers.
So some compassion is called for.