Here is the sentence:
In a more general sense, the later used phrase "reckless investors" could be regarded as a laughable contradiction in terms—something like "spendthrift misers"—were this misuse of language not so mischievous.
I understand what it tried to express, however, the last part "were this misuse of language not so mischievous" confused me a lot. I don't know how it can fit in the sentence structure in English grammar.
It should not be confusing: it is a particular (and more formal) construction for expressing a conditional clause (which you could call 'conditional clause without if').
..., were this misuse of language not so mischievous.
is equivalent to:
..., if this misuse of language was not so mischievous.
'Were' is an alternative form of 'was', in the conditional:
..., if this misuse of language were not so mischievous.
Usually, we pick up a conditional clause immediatly, as soon as we hear 'if'. In the other form, the giveaway is a verb in the conditional form:
If you had studied more, you would have passed the exam.
is equivalent to:
Had you studied more, you would have passed the exam.
