Yes, there is a difference, but as far as understanding what a person is saying, you can use them interchangeably. In what situation would you need to know whether it’s a countable or abstract amount?
Problems. “I have fewer problems than I did last year” means that I understand what my problems are or am tracking some of them and no longer have as many. “I have less problems than I did last year” is more vibes based and is a statement that this year seems to be going easier than last year went
I’m fine with the “less” and “fewer” distinction only being relevant in formal settings. People need to give up on correcting “10 items or less” signs, though. The change is already here.
Depends on whatever style guide and dictionary your work falls under, I suppose.
When I edited law reviews, we used Chicago Manual and Webster. We had secondary and tertiary references as well in case the primary was silent or vague. We also had our own list of style exceptions and preferences. But that’s law and policy writing.
On the grocery sign, or on things such as ads, that’s not writing, that textography. The rules don’t need to be formal on the sign. The word was chosen for space constraints. The word with fewer letters takes up less space. If all you do is read signage, fewer and less probably feel interchangeable. If you are reading law reviews and legal opinions all day, you recognize the number disagreement error, immediately.
The countable / uncountable element which creates the disagreement error comes from the dictionary. They are slightly different parts of speech even. Both are determinative adjectives but only one is comparative, by definition. Correct me if I’m wrong.
