I'm getting confused over the proper grammatical construction when starting sentences with prepositions. Since I'm using dual copies of MS Word, I'm getting conflicting advice from their already faulty spell checker. Word 2019 let's sentences like "So you finished your quest?" and "So what happened" pass unmarked, but when editors return the same document with edits (without changing those sentences), suddenly it makes them all as errors. It'll also flag the first is I dare to include a contraction (ex: "So you finished your quest?" is supposedly fine, while "So you've finished your quest?" isn't)!
Are fiction (non-formal writing) supposed to insert a comma for EVERY initial proposition, or is there a certain word/character limit exception?
Frankly, this is why I'd rather rip every goddamn spell checker out by their electronic roots and flush them all down the eToilet!!!