This is interesting way of thinking, and sounds almost something I could think 
but, maybe the guidelines are only for members, and the card registered by Postcrossing team is done in different role.
Like, I can’t fine a person if see them speeding but a police can do so.
I guess you mean “the second one”, not “the first one”
Also, the police can go over the speed limit in an emergeny, love the analogy! 
True, forwarding not being available is a valid argument. Not working properly, though, in my opinion, is not. Just as you should expect the whole postal system to work properly (although we know that it doesn’t always), you should be able to rely on a working forwarding service. If the feature is meant to cover up for a faulty forwarding service, it could as well cover up for any part of the postal system that may not work properly and register any postcard as received immediately when the address is drawn. Likewise, if the feature is meant to cover up for users not being able to collect and register postcards sent to them, it might as well do that under any circumstance and automatically register any card as received as soon as an address is drawn.
I guess my point is that the feature appears a to make the system a bit inconsistent in that it allows the recipient to register postcards prematurely (and thereby more or less violate the guidelines) during certain conditions. You may of course argue that changing address is an exceptional condition that requires special care, but I think that a user should be able handle the situation (see below) without the need for a system that registers cards before arrival, especially when some of those cards may not even have been sent.
Well, these are just my personal views and my personal preference is for a system without exceptions. It is not a big deal, but I would be interested in knowing the rationale behind such an exception, and whether there are others.
There are several ways: asking someone (if any, a familiy member, for example) still living at the address to hand it over to you personally or mail it to you, asking the new occupant at the address to hand it over to you personally or send it to you, intercepting the mailman on his route, setting your account to inactive before moving etc.
Maybe you change your point of view, when you are a bit more experienced and sent some cards to addressees in countries with a not so reliable postal service and they get lost, although the addressee set their account to inactive three weeks before moving, but you drew their address four weeks before their moving. Remember that cards to Russia, China, Taiwan, Brazil, Mexico etc. can take very long. And the postage for cards from Sweden to the rest of the world ist not really low.
I think in most cases people move to another town and do not know the people who move in after them. And the mail carrier is also a different one.
In the US the post office only forwards 1st class mail so postcards probably just get thrown away. Sometimes mail gets delivered to the old address; when I bought my house I collected all the old owners delivered mail and let them know. They would come by every few weeks to collect it but eventually told me to just toss it.
Well, if it is the case that you are not able to collect the cards sent to your old address in any way whatsoever, you should not use this feature, right? Accoring to @lavieay, it is stated that the feature should be used only if you ensure that you will get postcards eventually.
Sorry for going off-topic here, but I have also seen members from the US talking in the forum about getting their postcards forwarded… and it seems to work quite well. I think postcards are treated as 1st class mail too… or at least the ones that arrive from abroad (First Class Mail International).
I would feel very unfriendly if I let the cards get lost instead of having them registered by Postcrossing.
Your statement appears to equate postcards with postcard IDs. In my opinion, a lost postcards is a lost postcard, regardless of its ID being registered or not. Just to be clear and also in my opinion, a lost postcard is any card that doesn’t make it to the recipient, for any reason, including the sender messing up (illegible address, wrong postage), the postal service messing up (dropping it, shredding the card in a sorting machine), or the recipient messing up (dropping it, being unable to recover mail sent to their old address).
I myself would feel rather unfriendly if I gave the sender the impression that I had got their postcard when in fact I had not, or left them hanging wondering whether I actually got the postcard or not, which is the case for me right now. I don’t want to sound dramatic, but in a way it could be interpreted as if the would-be recipient of my postcard is saying I never cared about your postcard, but here, have an increased sent-counter and a freed up traveling slot.
Sure, eventually they may get back to me and inform me that the postcard actually did arrive and perhaps even respond to whatever I wrote on the card, but I wouldn’t have minded waiting until then or until the card expired properly, despite me being an inexperienced newbie with a measly maximum traveling count of seven. Right now, knowing that the recipient may or may not have received my card or that the may or may not receive it, is rather useless to me. But, yeah, I did use up that freed slot immediately 
You can assume that they haven’t received your card if the account is still there and the card was registered due to address change. If the account is closed, both may be possible.
But, since in your case, the account was closed, I think it’s actually technically the only option to register the card. Because the user won’t be able to register it anymore. It would otherwise be thrown into a black hole, more or less.
Sorry, I meant the local US post office doesn’t forward postcards within the US, at least mine does not…nice to know that yours does
Does the sender get’s a postcard back, when Postcrossing helped registering postcards? The mail doesn’t say:
Now YOU get a postcard back….
Yes it should, but I don’t know why it doesn’t say so in the message. 
Sometimes the sentence is missing from the email! This happens if, at the time this postcard was registered, you had already received as many or more postcards than you had sent.
I completely agree with you. One of my sent cards was registered by the system today. I sent it in February to a postcrosser within Germany who is still very active. When it took too long (after 2 months), cards within Germany usually dont just get lost, I asked the receiver if she might have forgotten to register. She replied, the card didnt arrive.
Today, after more than 300 days of “travelling”, the card was automatically registered. It did not arrive and the reason was not, that the address has just been changed. Perhaps we are too pernickety, but I rather don`t want this card among my sent ones (though it is a beautiful one).
I don’t think postcards are automatically registered without a good reason? Like problems with post office, theft, moving etc.