Brian- Sorry you had a bad experience at the park.
Vis has been poor and often is in the early summer due to plankton blooms, bat rays hammering the bottom, etc. In the park BOW classes also stir things up quite a bit. Not much we can do about the natural causes for that.
As for reserving space, during crowded times (summer weekends), it is first come first served. It sounds like you gave the other guy with the tarp plenty of room for separation. Don't see what his beef was. You say he had "local knowledge." Was he from the island or from the SoCal mainland?
There are often problems with divers who stand on the lower stairs to get their fins off. Three seconds is nothing. However, it is always best to walk up to the large flat step about 1/3rd of the way up the stairs so incoming divers can land while you are taking off fins. The one who complained sounds like she was a bit quick to judge though.
In general I sense a lack of courtesy in people these days whether they are divers or not. It is amazing how people will walk towards me four abreast on the way from Avalon to the Casino and wonder why I, with my up to 175# of gear on a hand cart, don't move out of their way (where to, I wonder?). Sorry that the lack of courtesy was evident that day.
The thing with your girlfriend and the stranger is odd as well. It wasn't me, was it (I do have a strong attraction to the Asian lady divers)? Seriously, just a lack of good manners on his part.
Come back in the fall when the weather is still great and the water warm but clearer!
