The +auto size font setting scales a bit weirdly in different situations

[MoerasGrizzly]

In FSO, by default, most fonts scale relative to the screen. For example, here's a mostly-retail screenshot (with only the font replaced to an OTF font) of 1024x768

And here's one taken with a 2560x1440 resolution:

However, things change a little bit when the auto size factor is introduced:

Text proportionally gets a lot larger when resolutions are increased, scaling seems to be applied twice - the scaling that +auto size is doing, and the scaling that's already happening to keep all the fonts the same size compared to vanilla interface elements.

Another problem occurs when Bitmap Fonts are used:

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It's a bit of an annoyance because +auto size is actually a really useful in situations like scripts rendering text to the screen. In FSO, by default, those don't scale at all. With +auto size, those texts scale like you'd expect, which makes things like configuring Axem's msgbox script a lot easier.

[wookieejedi]

Yeah as you mentioned, any font that the default UI uses should not be auto sized because FSO will size it twice (once for auto size and once for UI default). The core issue is that these are just two very different solutions/paradigms that should generally be kept separate by modders. In other words, any font used in the default UI (IE the first 3 fonts on the font table) should not be auto sized or auto scaled. Other fonts in the table around then be listed and those fonts should be used in scripts.