I've been thinking for a while now that it would be good for the EpiDoc Schema to explicitly disallow sigla such as square brackets, braces, parentheses, underdots etc in the edition div. This would be especially useful for students to realise that leaving square brackets in the text isn't "just as good" just because it appears in the output untransformed.
(Additionally, we might write transformation rules that do something ugly with them, to further dissuade such bad practice.)
The Schematron should be simple to write--I'm happy to take this ticket on if no one objects.
I'll have a look at this for the next release.
Not actually sure this is a great idea. Underdots, at least, might turn up as Unicode codepoints in transcriptions of languages such as Sanskrit. Need to survey Markup before implementing anything this drastic. (Punting to future milestone.)
This might better be moved to a separate "EpiDoc" Lint Schematron. There are scripts and script transcription conventions that legitimately use these.