No think about it, if it would penalise a site. Then if i had 10,0000 posts i could link to any website and cya it would get penalised. So No!
Basically you will get links from any thread that you posted in if it is crawled. What you are saying makes sense only because many threads are no longer crawled. If they are bumped, your link will be picked up when Google crawls it.
And from another point of view: Google links analysis are basen on many elements including IP addresses where those links are placed. If we talking about signatures, it could be considered as sitewide links, which are fine in some way for SERPs, but not much more than single links from unique domain (and with related content and not spammy, etc, etc...). So, it is obvious that system have to be enough sophisticated to distinguish different situations and act more/less right with the general rules.
never heard about this before, and i don't think it's true.. what if i am a style designer for DP and i put my link in style, all DP pages will have my link in same time! whats the problem?