Per my reading of the explanation here hotness score of successive questions from same site is penalised by 2%.
Taking into account that there could be no more than 5 questions from the same site this means that maximum possible penalty is 8%. I am looking for an explanation of how this is supposed to make a meaningful impact, because at the first glance, it looks too small for that.
To have a better idea of what possible impact it could have I sampled score of several questions in some snapshot of hot list. Hotness score values I observed were 46.422, 17.269, 10.194, 7.485, 5.825, 4.658, 3.891 for questions ##1, 16, 31, 46, 61, 76, 91 respectively (for that sample I simply picked top question from each page of the hot list configured with pagesize 15).
Distribution of the scores in above sample suggests that even maximum of 8% would "push" the penalised questions less than 10-15 places down in the list, how is this supposed to make a difference (particularly since questions from the list are anyway randomly shuffled before getting displayed in the sidebar)?
Alright, that limit of 5 is relatively recent thing - but closer look at sample distribution of scores suggests that even without it, even if system allowed 10-20 questions from same site like it did before, the effect of penalty would be negligible.
Max penalty in this case would be 20-40% - meaning that question would still have solid chance to stay in the list and get shuffled to sidebar - and this is the most penalised case, for other questions from same site the difference would be even less than that.
I really don't understand how this parameter is intended to work.