When the “Refer to encoding declaration in document” option in the Format settings pane is selected, CotEditor reads the following types of encoding declarations (if present) — charset=, encoding=, @charset, encoding: and coding: — when opening a file. If written properly, these declarations are used to determine the file’s text encoding.
A declaration can be anywhere in the document, the one either in the comment area or in a plain sentence is detected. When you want to use a phrase such as “charset=UTF-8” even though your document’s encoding is not UTF-8, you need to put an actual encoding declaration prior to the phrase, or, unselect the “Refer to encoding declaration in document” option in the Format settings.
charset” or “encoding.”charset=” or “encoding=” can be without double-quotes (") around.