I have just learned that there are some adjectives with optional umlaut-ification (e.g. rot) as opposed to required or prohibited (in comparatives and superlatives).
So... is there some general sense of the optional effect? Like is the decision to use the optional umlaut more old-fashioned or formal or more regionally a trait? [I am trying to make sure I don't lose my Kinderaustrian, in the course of learning German. ;)]
FWIW, below site says that it is unusual to decide for the optional umlaut. So is it OK, if I just ignore them in my own writing, speaking? Just knowing they are out there in some texts, speech, for recognition?