Is atheism a scientific perspective?

[Angrboda]

The first part of your argument seems really shallow. I think you know that we are not saying that "it looks designed therefore it was". It is "despite thorough search for another cause, only intelligence is a known cause that can produce what we see in designed systems". It is not that we are just appealing to our initial intuitions. These conclusions come after careful studying of the systems and proposed explanations.

(emphasis mine)

But intelligence isn't a known cause for the type of complexity we see in the cell, so your argument can't be valid. No human on earth has the intelligence to create something like the cell. So you're just jerking off by saying that intelligence is an adequate cause for what we see in the cell. (And I'll note that what you've stated isn't an argument for your conclusion.) Even if properly stated, it's also still an argument from ignorance and fails on that count.

Your argument seems to be "because in the past we have seen apparent design turn out to be illusory, all apparent designs are illusory". 

No, my point is that if your procedure produces false positives, then it can't be reliably used to infer design.

And the functionality of the wing is the result of elaborate informational output by the cell.  Obviously the wing itself is not information, but I think it is impossible to argue that its functionality is not the result of information. And you say "For if it is even possible that specified information can arise natrually, it's no longer a flag for design." You seem to be suggesting that if it's possible that something arose without design, then it was not designed. This is illogical for several reasons.

No, I'm pointing out that if a particular property, specification, isn't exclusive to designed things, then it can't be used to determine whether the item was designed or not. It provides no probative value for the inquiry under consideration. If it being specified simply means that it was either designed or natural, if you can't rule out it being a possibility that the property has a natural cause, then it cannot be used to make an inference of design.

Also, we have no good reason to assume that it can arise without the help of a designing intelligence. If you have a reason that you think it was can you provide it?

Doubling down on the mere possibility that feathered wings evolved will not save your argument. But whatever. It's telling that you have to deny established science to make your inferences work at all.

You say that abiogenesis is a significant possibility, but I think that's just wishful thinking. We don't have to assign probability to design either, because we know based on repeated experience that intelligence is adequate.

Adequate for what? What exactly are you suggesting we are "seeing" that justifies this claim. That's why I went through the laborious exercise that I did, to point out the need to be specific about what properties indicate design. If you can't specify the properties which indicate design, then you've got nothing. As pointed out, specified information, even with your vague definitions, simply doesn't work.