I could take a look at this sometime in the next few months but I'm not sure what do you mean. In particular:

1. Is the parser doing partial parsings of every inserted/removed character or line in a more or less complete syntactical environment around the insertion/removal?

2. If the parser identifies a block how is it in a better position to flag it as outdated regarding fontification? Do you mean completely circumventing the search based font lock mechanism with its multiline property and region extensions? That is, directly setting face related properties and forcing a refresh of the region?