I’ve seen a few articles that talk about the risk of placing non-vapor permeable items against exterior walls in hot/humid climates. 

The risk is that in the summer months, the interior surfaces are cooler/dryer than the exterior and so vapor drive is inward, and so vapour will condense on the back of the non-vapor permeable item. 

So for example, don’t put up vinyl wallpaper, mirrors that are right up against the wall, etc. as vapor will get trapped and mold will form in behind there.

But what about showers that have tile walls, or bathrooms that have tiled walls from floor to ceiling. Presumably most of these ceramic/porcelain tiles are vapor impermeable.

Given how many houses have bathrooms on exterior walls (a window in a bathroom is a nice feature!). Is this a big risk? 

Building Science Corp. explains some of the issues here.

https://buildingscience.com/documents/building-science-insights/bsi-130-hotel-mold