My first reaction is to say that this is a bad idea as I and many others often read old nodes and vote on them too. However, it occurs to me that anything deserving a -- that is over a month or even just a week old has probably got sufficient -- to keep the coffin lid nailed shut, so maybe this isn't a bad idea after all. Personally I don't think I've ever downvoted a post that is more than a week or two old.

On the other hand (I always carry two), I don't like solutions where there isn't a real problem. I think the actual number of incidents of a person being singled out and bulk downvoted is very small and we have to consider whether such a strict voting limitation is warranted. Perhaps a better solution would be to detect multiple downvotes from a single voter within a short period of time, on nodes which had postitive rep. to start with... but compared to your quite simple solution this better protection would probably give the creator a fit!

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I'd like to be able to assign to an luser