It is not just about courtesy either, there are practical implications. Many topics from the Card Identification forum get moved to the forum for the particular set they are about, especially if the set gets added to the database because of the discussion.
If you add a post about another set to that thread, that information will be harder to find later because it will be associated with the wrong set. Best practice for identification requests (and new discoveries) is to keep the sets in separate threads. If you think there is some similarity and the discussions would benefit form participants being aware of both threads, you can post a link to one in the other. Just make sure you're clear about why you think the discussions pertain to each other, a "Hey look at my topic too" post will be viewed as hijacking.
I hope many readers understand this reasoning, I don't mean to just 'pile on' to you RefsInTheBack.
Ted Musgrave card collection 98.9% Complete: Cards Known: 1013, Cards Owned: 1002
I prefer the company of people who disagree with me for the right reasons over the company of those who agree with me for the wrong reasons.