This is also a reason that I don't like using editor features that automatically close parenthesis or quotes when you type the opening pair. That may make the expression syntactically correct, but semantically incomplete and the burden will be on me to notice, since syntax highlighting won't help me then.
I'm also not a big fan of overly eager syntax checking because I tend to compose abstractions on the fly, leaving a statement incomplete while I flesh out a dependency, or vice versa. Syntax aware indenting usually breaks badly in this situation - I generally prefer dumb indenting, with an opt-in block or file format option for where I want to fix code over a large area. I've had big fights with Emacs over this; it almost always does the wrong thing by default, whether it's indent location, continuation indent, mixing tabs and spaces in the indent, etc. About half my .emacs is replacement indentation functionality and configuration per mode.
I also don't like auto-completing parentheses, because it puts text ahead of the cursor on the current line. That's a PITA because the editor almost invariably doesn't know when I want to complete the expression or how. Eclipse is the worst at this (it's actually not possible to turn off in a sane way). It interprets RET as completing the expression when I want a line break inside the parens, and I'm constantly having to go back and forth to work around its mistakes.
Funny, because I dislike having syntax errors highlighted for the exact same reason. If I'm typing new code, I like to keep my thoughts on the reasoning behind what I'm typing, and leave it until later to "clean up" the code and get it syntactically correct. Having big red highlights around code that I haven't finished writing yet is a huge distraction... the editor seems to be beckoning to me: "Stop typing and close that paren! Why are you still typing! It's not corrreeeeect yet!!!". And usually it's enough distraction to cut off a good train of thought.
It gets worse when the editor starts complaining about full compilation errors, like calling functions I haven't written yet. When I'm in a more "creative" part of my coding (like when I'm doing lots of brand new functionality), there's a certain ordering of what I write first and what I fill in later, and having an IDE yell at me the whole time is just tiresome.
> What do I miss? Syntax highlighting hinting that I made a dumb typo (importance is directly proportional to compile time or speed of running syntastic).
when someone builds something they often 'hard code' their own specific interests into the thing
so let's say i am like you, and only want the comments highlighted.. if the highlighter i am using fails to allow me to alter it from the user side of things i'll have to dive into the source
if it is closed then i have to take the time to build my own wheel
if it is is open, but after investigation i find the functionality is hardcoded, piecemeal, and highly specific then i have to take the time to build my own wheel
this is an overly simplistic example of what i am trying to illuminate but from a user's perspective there is a huge difference between these equations:
print(51)
n=3*17
print(n)
a=3
e=17
print(a*e)
a=sys.argv[1]
e=sys.argv[2]
print(a*e)
for highly configurable designs just pulling flags from the command line will get out of hand quickly but it would be superficial to have a function that allows the user to see the programs state and alter it to their needs
Making comments distinct from normal code is nice because you can easily alternate your focus on one or the other while reading through; and you're not likely to accidentally read commented out code as actual code. You're also not going to forget to close out your comment, for languages with paired comment delimiters.
Making strings highlighted makes it a little bit easier to ensure you're terminated your strings, especially in edge cases around escaping and quoted quotes (for languages that have a choice of quote characters).
Semantic highlighting - distinguishing identifiers based on their definitions - is a seriously niche win most of the time, where you're spending ever increasing amounts of CPU for a marginally actionable hint.