The Rama wrote a series of glosses to the Shulchan Aruch to reflect standard Ashkenazi practice, as the Shulchan Aruch was weighted towards the Sephardim. These glosses have been reprinted in almost every edition since then and are introduced in the text usually with a font change and the word הגה=gloss. Sometimes, one comes across a gloss that has a different font, but is not preceded by the word הגה. Sometimes these anonymous glosses are in parenthesis and sometimes not. (One such example is here.)
Who wrote these glosses? Was it the Rama? Was it a later publisher? If they are the Rama's, why don't they start with the usual הגה?