Bringhurst urges us in Chapter 10 of The Elements of Typographic Style: Version 4.0 to fix the font files if needed. See below a summary of the chapter using the section titles.
Bringhurst suggests to modify the font file so the fixes are done forever. But I think that for some fixes we can use feature files in LuaTeX. This can make easier to transfer projects from computers with fonts installed system-wide.
I ask for help to identify what can be corrected using feature files and show an example file. (Would it be better to make this question a comunity wiki?)
List of possible issues to be fixed
Sometimes the glyphs are completely wrong. Usually due to missing glyphs taken from other fonts. In this case the only possibility is to use a font editor. Not possible with feature files.
Hinting is not an easy process and sometimes is wrong or missing Altogether. In this case the only possibility is to use a font editor. Not possible with feature files.
Some characters' vertical position (specially +, -, dashes, ...) could be improved. Is it posible to fix it with feature files?
This is the blank space at the right and left of the outline of the glyph insie the box. Bringhurst says that he has to fix these values usually to fix the space between letters and puntuation symbols (He describes his style in this regards as a halfway between british and french typographic traditions). Can/Should it be done with feature files? (The
microtypepackage can do the french typeseting style. Does it use kerning correction for that?)
Some characters could be in an inappropriate encoding position. I guess this can be fix with a GSUB rule.
What to say about bad kerning, that the audience of this forum doesn't already know! This is an easy one; I can even answer myself :-)
Summary of Chapter 10
10 Grooming the font
10.1 Legal considerations
10.1 Check the license before tuning a digital font
10.2 Ethical & aesthetic considerations
!0.2.1 If ain't broken...
10.2.2 If the font is out of tune, fix it once and for all
10.2.3 Respect the font first of all, the letterform second, the type designer third, the foundry fourth
10.2.4 Keep on fixing
10.3 Honing the character set
10.3.1 If there are defective glyphs, meal them
10.3.2 If text figures, ligatures or other glyphs you need on a regular basis don't reside on the base font, install them there
10.3.3 if glyphs you need are missing altogether, make them
10.3.4 Check and correct the sidebering
10.3.5 Refine the kerning table
10.3.6 Check the kerning of the word space
10.4.1 If the font looks poor at low resolutions, check the hinting
10.5 Naming convention