For flagging: use the Very Low Quality flag for answers which are complete nonsense, such as
incoherent gibberish
anything not parseable as English text
answers posted in another language
as well as answers that are wrong, or based on non-mainstream physics, that you think are flat-out incorrect, so completely incorrect that no amount of editing can make it useful or constructive, and so completely incorrect that it is actively harmful to the site and its standing.
Do not use this flag for:
followup questions