Saying that XT is an altcoin is factually incorrect, this is also a false narrative. Bitcoin XT is compatible with the Bitcoin blockchain. The fork will only be triggered once a majority of mining power supports it, which means that post fork Bitcoin XT will also be compatible with the largest surviving Bitcoin blockchain. There is a fundamental difference between a blockchain fork and an altcoin. It would be wrong to equate these two separate phenomena.
That entirely depends on what the actual definition of altcoin is, this is an evolving space and definitions are being settled.
If Feathercoin is an altcoin then so would be XT.
If we define an altcoin as being a blockchain that is incompatible with the main Bitcoin blockchain then according to this definition Bitcoin XT is not a altcoin.
But that's not the definition many of us go by, certainly not me. By that definition Bitcoin today is an altcoin of Bitcoin from 2012.
You can look it up in the wiki linked above.
It seems like you are just appropriating the term in order to use it to construct this false narrative. Furthermore according to this "wiki" that you have linked the definition of an altcoin is that it is incompatible with the main Bitcoin blockchain. Therefore according to that "wikis" definition of an altcoin Bitcoin XT is not an altcoin. Therefore this wiki is wrong, it is even self evident based on their own enclosed reasoning.
If the definition of an altcoin is not that it is incompatible with the main Bitcoin blockchain, please enlighten us with your definition of an altcoin instead. Then we can apply that definition to Bitcoin XT and see if it is consistent.