[Ha Ha Thats Very Logical]

But if the rules of a designer produced everything in the world by natural processes then either the processes are directed according to those established rules and hence are not natural and only have the appearance of naturalness or an appeal to a designer is superfluous.

I'm not sure what you're saying in that last part. But when you say "the processes are directed according to those established rules and hence are not natural," would that also apply to the formation of a thunderstorm? Is that not natural because it's "directed" according to the established rules? I've said before, I'm willing to grant that evolution is no more natural and no more unguided than the formation of a storm.

The whole idea behind naturalistic evolution is that none of it gives evidence of a designer and needs none as all results can be explained by natural processes.

Well, none of it gives evidence of a designer any more than all of it gives evidence of a designer. Lowercase intelligent design can credit a designer with setting things up to operate on their own just fine; Intelligent Design demands a designer that fiddles every so often to get the desired result. Intelligent Design is about special cases; intelligent design is about every case.

But would they argue for it?

Some would, and have, right here on FR.

[count-your-change]

One, you misstate what I.D. is about as I posted what their ideas are (in the name of accuracy not support.)
In fact the I.D. folks go to some lengths to avoid a designer let alone one that fiddles around in creation every so often.

Hence my question about how a person looking at some object would determine whether it is the result of intelligent design by someone or just a natural oddity.

What sort of mental process would we use to reach a conclusion? What would we look for? What general characteristics are unique to intelligently designed things
so that we can separate them from all other things?

That's what intelligent design and I.D. encompasses.