The minus, double-quotes and parentheses work in many situations, but not in all situations, all of the time. They used to be deterministic. Just this week I found some more searches where wrapping a specific two-word phrase in quotes would actually remove half of the auctions that had that exact phrase in the title. And others where minusing out a term stubbornly refused to remove it.

The worst thing is when you are searching for an item, but most of the listings are those "multiple different specification" listings. e.g. a seller has 8GB, 16GB and 32GB USB sticks. It's almost impossible to compare listings and the price you see is clickbait because once you click through you find the thing you were searching for is several times higher. I wrote a bookmarklet to remove all these, but that's not ideal because it can over-correct.