'eBay's search can only be as good as the data supplied by sellers…' simply isn't true, as everyone with any knowledge of data processing was taught in lesson 102, if not 101.
By that, I mean that if you search for a red widget on eBay, eBay will return listings where sellers include those specific terms in the title or item-specifics, whether or not the items being sold are red or even widgets at all. Not all sellers are making every effort to ensure that the keywords that appear in their listings are limited to appropriate ones, as they should. Whether any specific search succeeds depends on the efforts of eBay programmers, individual sellers, and the user searching.
Not long ago, we could use standard (prolly HTML; I don't mind) search instructions to include or exclude various terms.
Do you mean regexp? eBay uses its own syntax, but you should still be able to include or exclude various terms. If you use the Advanced Search page you can do that using various fields, but many of the same results can be obtained by using specific search commands directly in the search bar of a standard search -- for instance, by using a minus sign to exclude a keyword, or quotes around words or phrases to get exact results in order with no substitutions or intervening keywords.
No wildcards any more since 2012, though, unfortunately.
If you are having problems searching and want help, please provide an example of a search that is not working and describe how you think it is failing; someone may be able to suggest an alternative search that better meets your needs.
