I'm reading through one of the links and this caught my attention:

>For example, to sack / fire / dismiss is pok tao lo 卜头路 — (spoken by the mother), so natural, more emotional than when you say kāichú 开除 (as in Mandarin).

This sort of illustrates my point, "卜头路" is a transliteration of hokkien using Mandarin pronunciations, so as written, it wouldn't be understood by anyone who doesn't speak hokkien. An apropos analogy is "bone apple tea", if the listener doesn't know "bon appétit", then it makes no sense whatsoever.

Yet still Hokkien speaker understands what "开除" means and use it in more formal contexts, albeit with a different pronunciation from Mandarin. In this way, written Chinese can be understood by people who speaks different dialects.