I came across the following sentence while reading:
Don't cough more than you can help.
I cannot make any sense of it. Can you help me to understand this sentence?
It does make you wonder who spends time coughing optionally.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
People who do so rhetorically?
It does seem strange when worded this way. I would expect "Don't cough if you can help it", meaning "Don't cough if you can possibly avoiding doing so".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.