Not to beat a dead horse (or maybe to beat one), but...
As stated above, I found that the information in the normative principle definition -- The normative principle teaches that whatever is not prohibited in Scripture is permitted in worship, as long as it is agreeable to the peace and unity of the Church. In short, there must be agreement with the general practice of the Church and no prohibition in Scripture for whatever is done in worship. -- was added to Wikipedia by an anonymous editor on 16 September 2013. I traced this back as being brought over from the article on the regulative principle of worship, which information was added on 1 August 2005 by editor Mkmcconn/Mark. After this I did Google and Duck Duck Go searches for these two phrases:
"so long as it is agreeable to the peace and unity of the Church"
"agreement with the general practice of the Church"
Of the first, all the hits I noticed lead back to the Wikipedia article. On the second, I found the phrase "agreement with the general practice of the Church" used once that was not connected to the Wikipedia article. It was used by Edward Burbidge in
Liturgies and Offices of the Church for the Use of English Readers, in reference to the practice of communion in the Church of England. It seems to me, lacking further confirmation, that a Wikipedia editor added his own opinion or explanation about the idea of the normative principle of worship, and this has been accepted without question by various writers who have quoted it as a source.