@ne555
Thought experiment.
There exists 10 forums, each with 1 helper, and 1 newbie joins to ask a question.
Thus, 10 helpers in total help 10 newbies quickly as it's all done in parallel.
Everybody is happy. All newbies got an answer, and helpers didn't waste their time.
vs
There exists 10 forums, each with 1 helper, and 10 newbies join all the forums to ask a question.
Each helper now faces 10 questions, an awful lot of extra work, and a silly guessing game as to whether it's even worth answering the question because it's well known that the newbies cross-post like crazy. Some questions get answered more than once, and others are ignored completely.
Almost nobody is happy with the outcome.
The mentality of cross-posters being:
1. I'm a special snowflake worthy and demanding of your attention.
2. This is an urgent problem, so I maximise my chances by spamming forums.
See also
http://www.catb.org/esr/faqs/smart-questions.html#forum
http://www.catb.org/esr/faqs/smart-questions.html#urgent
So, I cross-link whenever I see it for the benefit of the regular helpers. At least then it's possible to quickly decide whether it's worth the time investment in replying. There's no point spending effort if there is a perfectly decent response elsewhere.