In the last couple of months I've been following the appearance of <nowiki> in the Hebrew Wikipedia.
One of the most common reasons for its appearance is that people type '' instead of " - that is, two apostrophes instead of a single quote.
This made me notice that neither '' nor ''' produce a "Wikitext markup detected" warning bubble.
Is there a reason for not showing this warning for these pieces of wiki syntax? Outputting <nowiki> when people write them in VE is the right thing to do, but usually they are not supposed to be written at all. (The only notable reason for writing them I can think of is in the Neapolitan language, in which two consecutive apostrophes is a part of the orthography; for an example, see [[ https://nap.wikipedia.org/wiki/Terra_d%27%27e_fuoche | Terra d''e fuoche ]].)
If there's no reason for this, then the bubble should be shown.
Another option is to auto-replace '' with " while typing and let people undo it, as suggested by @Pginer-WMF (but Neapolitan will need special handling).