If an intransitive verb is one without a direct object, then "The painting was displayed in the Louvre" surely counts as intransitive? Unless you count "to be displayed" as a different verb from "to display", I guess.
I often interact with (specifically Japanese) people learning English and I've come to conclude that the whole transitive/intransitive distinction is quite fluid in English. Japanese is much more clear-cut in most cases thanks to having a direct object marker (を) for transitive verbs, as well as most often having distinct transitive/intransitive verbs (eg, 現す/現る) that form pairs.
As for the Oxford comma, the article did pick a good example of when it's useful. It's not always the case, though. My preference is not to use it in general, but only insert it if it's necessary. In many cases it can be avoided by reordering the terms. As for shift-reduce errors, English grammar isn't LR.