The problem with the smart quotes <q> </q> is that if one is missing, or a spurious one is added, the error is perpetrated throughout the rest of the game (or until a compensating error is located). The purpose of quoteFilter is (a) to report such errors (to make them easier to fix) and (b) to prevent them being propagated beyond a single turn. In the main this works by having quoteFilter take over responsibility for turning the <q> and </q> tags into the appropriate HTML entities rather than leaving it to the HTML rendering engine in the interpreter. The quoteFilter OutputFilter keeps its own track of whether a double quote or a single quote is rquired next, and resets this count at the start of each turn.

quoteFilter :   OutputFilter   InitObject