That sentence, taken as it is written, would imply the exact opposite to me. There may be dialectal differences, of course, but if there are then people are bou

That sentence, taken as it is written, would imply the exact opposite to me. There may be dialectal differences, of course, but if there are then people are bound to misunderstand this. If you cannot understate something, then any statement no matter how bad (for example "it is mediocre") is likely to be an overstatement. That's now how you would think of something important. Double negations are always tricky. "Can not be understated" can more clearly be written as "easy to overstate". English slang is full of double negations. A sentence such as "I didn't do no harm", which would absolutely mean harm was inflicted, can mean the opposite. So it may be good to avoid them as to not confuse non native speakers.