It's just a parsing error. "in-" is also a prefix to create verbs from a name or another verb like inhume, inflame, induce, incite, inject, infiltrate. Inflammable is (inflame)-able and not in-(flammable)
There are many counter-examples to your examples, such as “direct” and “indirect”, “humane” and “inhumane”.
The words used should be clear in their meaning. “Inflammable” is ambiguous, and it makes a great deal of difference which meaning is intended.
Flammable is unambiguous, as is non-inflammable. I’m forced to use these. Personally, I’m more in favour of flammable (able to catch fire) and inflammable (not able to catch fire).
I agree, but it’s ambiguous, hence the problem.
There are many counter-examples to your examples, such as “direct” and “indirect”, “humane” and “inhumane”.
The words used should be clear in their meaning. “Inflammable” is ambiguous, and it makes a great deal of difference which meaning is intended.
Flammable is unambiguous, as is non-inflammable. I’m forced to use these. Personally, I’m more in favour of flammable (able to catch fire) and inflammable (not able to catch fire).