Many years ago (when a QC but much younger and less experienced than I am today) not flying QF but wanted to see the then refurbished QF international MEL lounge and was refused by relay (from the older lounge dragon who was a foot away from me with her head down and wouldn't meet my gaze to the younger sentinel).

Very unpleasant experience then. Thankfully all ok since with QF, BA, CX.

Alaska Airlines still an issue as they charge admission (US$25) when flying with them on discounted first class tickets but admit free for full fare paid first. In general American lounges well behind rest of world.