While working out #9481, @anntzer and I have come to the conclusion that the hinting_factor setting is a relic of a different time when FreeType rendering was not so great. In essence, it causes horizontal rendering to be done at high resolution and then scaled down. However, it is not entirely clear that it is still necessary to do so.

Additionally, tests disable hinting but enable this factor (at 8x scaling). The default style enables both hinting and this factor. This makes it a bit difficult to say what the end effect would be overall.