I assume this is directed at me, even if it isn't I'll give a reply and then await the backhanded comment you have the custom of giving my Christian friend.
Firstly the NWT translators do not go around changing scripture just because certain scriptures do not fit into their ideology. Nor have they changed any scripture, rather they translate scripture according to the context and grammar of any given passage, the only time they have added things into scripture is when they insert the divine name YHWH into the NT, but give reasons as to why.
In regards to John 20:28 the text is no more troublesome than 2 Cor 4:4 is troublesome for either you or me. As I have mentioned to you before Jesus is God in a sense, he simply isn't the one God, since the 'one God' is only ever mentioned as being the Father. In 2 Cor 4:4 Satan is called "ho theos" of the world, or better put, "the God" of the world. Does the fact that Satan is "the god of the world" demonstrate he is the 'one God', no. Likewise, does John 20:28 necessitate that Jesus is the 'one God' because Thomas says that he is the 'God of him", no, since Jesus is a God.
As I've made clear to you before, the bible states there are many gods, but to the chsritians, only one God the Father. Jesus is rightly one of these Gods in scripture, as Isaiah 9:6, Hebrews 1:8 and John 20:28 express, he simply is NOT the "one God", since only the Father is ever spoken of a the unique 'one' and only God in the ultimate sense, hence why Jesus said in John 17:3 to the Father that he is "the only ture God". 1 Cor 8:4-6 states, "there is no God but one. 5 For even though there are so-called gods, whether in heaven or on earth, just as there are many “gods” and many “lords,” 6 there is actually to us one God, the Father.."
Again, other beings are called Gods, Moses is called God (Exo 7:1), Angels are called Gods (Ps 8:5, cp Heb 2:7), Humans are called Gods (Ps 45:6, John 10:34). Beings, when called God, does not necessitate that they are the 'one God', but if other beings can be called God in a sense how much more so can Jesus who has been appointed above all things bar the Father, rightly be called God. The fact remains, despite Jesus being called God, like everyone else who is referred to as God, he is not the 'one God', only the Father is.
(1 Corinthians 15:27, 28) "..For God “subjected all things under his feet.” But when he says that ‘all things have been subjected,’ it is evident that this does not include the One who subjected all things to him. 28 But when all things will have been subjected to him, then the Son himself will also subject himself to the One who subjected all things to him, that God may be all things to everyone.."
Insert crude comment below *v*