God is entitled to add to His own word whenever He pleases. It never ceases to amaze me how many people feel totally justified in saying it's time for Him to shut up.
No one, absolutely no one, said that God can't reveal His word. What was said is that God does not want
man adding to His word. God's word is a lamp unto our feet.
Every word of God is pure: he is a shield unto them that put their trust in him.
Add thou not unto his words, lest he reprove thee, and thou be found a liar.
(Proverbs 30:5-6)
The words of the LORD are pure words: as silver tried in a furnace of earth, purified seven times. (Psalm 12:6)
Then understood they how that he bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and of the Sadducees. (Matthew 16:12)
Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all long suffering and doctrine.
For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; And they shall turn away their ears from the truth, and shall be turned unto fables. (2 Timothy 4:2-4)
If what some call modern revelation, is not God's word, it will most likely contradict what He has already given.
And the brethren immediately sent away Paul and Silas by night unto Berea: who coming thither went into the synagogue of the Jews.
These were more noble than those in Thessalonica, in that they received the word with all readiness of mind, and searched the scriptures daily, whether those things were so. Therefore many of them believed; also of honourable women which were Greeks, and of men, not a few. (Acts 17:10-12)