Breeno,
dragging up an old thread can be okay in some circumstances if you have something of real importance to add to the thread, but in general dragging up a thread that is more than a month old is unacceptable.
In this case, the posts refer to rules that are no longer valid so people clicking on this thread will be completely confused.
Here are some further guidelines on when it is acceptable to perform 'thread necromancy' and when it is not.
Thread necromancy is bad in some circumstances and it is fine in others.
Bringing up a year-old thread discussing rumors for an upcoming codex that has long since been released just to add a random quip about what you think of the codex is frankly unacceptable.
On the other hand, dragging up a year-old fluff thread to add some information you found in an hard to find WD article, for example, would be fine.
So the two things to consider are:
1) How topical the conversation in the thread is. The more topical it is, the less appropriate it is to drag the thread up.
2) Do you have something of vital importance to add to the thread? If you honestly do, besides just an opinion or comment, then it is more appropriate to drag the thread up.
The reason other members tell people to use the search function isn't because they want you to go ressurect an old thread, but rather you can go read the old thread and find the answer to your question. There is a lot of information that can be found on any forum through reading old threads as opposed to creating a new one that covers the same topic.
So in short, if a thread is more than a few weeks old you probably shouldn't be dragging it up if it is in the News&Rumors, Dakka Discussions, YMTC, etc.
Forums like modeling, fluff and tactics (to a lesser degree) are a bit more lenient to this kind of thing, but only if you have something substantial to add to the thread (i.e. you read every post in the thread and have found that a vital piece of information was never included in the thread that you think needs to be added).
In the future please use greater discretion when posting in old threads. If you are in doubt feel free to
PM a moderator to ask them if it would be acceptable.