By and large the only problem abandoned questions cause is that if there's no response with an upvote, it will be recycled to the top of the list every once and a while.
I had a look at the questions you mentioned. Wow! There's a lot of them, and the majority have no responses, and little if any comments of substance. I voted to close as no longer relevant, at least for the ones that garnered no interest at all. If nobody agrees with me then no harm done and my votes will disappear in a few days.
]]>@Will, the questions are not off-topic by themselves (they are NOT typical undergrad level). I probably would not notice it if there were not so many posted recently. On cstheory we have a little bit stricter policy and expect the OP to explain the motivation for the question and what they have done to answer it by themselves (particularly for questions in complexity since it is easy to generate difficult complexity theory questions, e.g. "What is the relation between complexity classes $C$ and $C'$?", "What are the consequences of $C$ being in $C'$?", ...). Probably with a little bit more effort the posted question can be turned into interesting and good questions.
@Anton, maybe we can politely suggest that they register and use real names? Also we can ask them to improve their questions by adding a motivation section explaining why they are interested in these questions and what they have tried to answer them?
@Henry, I agree that they don't look like undergrad homeworks, but I have seen instructors giving these type of questions as assignments in graduate courses. Still I am not sure if that is the case here, your theory is also reasonable. I just posted a comment to the last question linking to this discussion. (side note: I don't think that is true in general, some TCS researchers consider themselves computer scientists, others consider themselves mathematicians, and most consider themselves both.)
]]>On your actual concern: I've often wondered why people bother posting these types of questions here when the cstheory.stackexchange.com site seems a far better fit.
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