The phrase "once again confirmed" is correct and usable in written English.
You can use it when you want to reiterate something that has already been previously established as true. For example: "The results of the second test once again confirmed the findings of the first study."
"Gerhard Richter's international appeal as one of the hottest contemporary artists was once again confirmed this evening".
"Khandita" once again confirmed Ms. Sen as a great actress capable of conveying several layers of emotion at once.
Ahead of the final pairing, Englishman Luke Donald once again confirmed his status as the European most likely to win a major.
This week, art sales in New York once again confirmed the contemporary market is booming – it was apparently impervious, at the top level, to the financial crisis, and now that America's economy seems to be bubbling happily away, collectors are more enthusiastic than ever.
The result has once again confirmed the appropriateness of using Theory of Planned Behavior to predict entrepreneurial intention.
He also once again confirmed that the search deals with both Microsoft and Google are bringing Twitter money, though he declined to state how much.
HTC once again confirms its position that its phones do not make use of the teaching of that patent.
The figures once again confirm how far behind the rest of the UK Scotland is on overall longevity.
Mr Nonaka outfought him at every turn, once again confirming his reputation as the hardest man in Japanese politics.
And it once again confirms the UK's position as a world leader in bringing the latest advances in medical technology to patients".
"Sydney is the place to be this weekend – once again confirming our city as the home of major events and Australia's only global city," O'Farrell said.
