First a little information for those not familiar with open cell wetsuits. The interior of an open cell wetsuit is raw smooth neoprene. When smooth neoprene is dry it clings to skin, it's impossible to get into a dry open cell suit. Open cell wetsuits require lubrication to put on, as simple as water and hair conditioner. Once wet they go on much easier than a double lined scuba suit.
Divers who come to Freedive Store for an open cell wetsuit will normally want to try it on and make sure they get the right size. I'm pretty good at recommending the right size suit based on the person's appearance, normally I get it right the first try. Beats washing and drying suits after..
Experienced divers know the deal and have no problem getting into a lubricated wetsuit. Those new to it are sometimes hesitant. For this reason for a short time I used to let people try the wetsuits inside out. I know this is how it's done in some other dive shops. I stopped letting people try on suits inside out fairly quickly for the following reasons.
First reason is the suit is much more likely to be damaged. Even trying it on right side out I have to watch inexperienced guys closely. They tend to grab the open cell interior and pull the waist of the wetsuit down, putting tears in the neoprene, and the same thing happens when they take it off. To prevent this I always explain how to grab the lined neoprene exterior only. When the open cell material is on the outside it's almost guaranteed they'll put a tear in it.
Second reason is that an open cell wetsuit is all about comfort, and the contrast with a double lined scuba suit will be dramatic for those trying on open cell for the first time. If they try an open cell wetsuit inside out with the Lycra exterior against the skin, it will feel like a double line suit. Additionally a lined suit will never settle into place like open cell, it will always pull and constrict.
Simply put if you don't try on an open cell wetsuit as it should be worn, you'll never get a true idea of how it fits and how comfortable it is, and you're very likely to damage it. Because of this I never let anyone try a suit inside out. I use unscented hair conditioner for lube, add warm water for comfort, provide a private change room and fresh towels for after the fitting. Damn it sounds like a spa.. 
I've had guys ask to try it on inside-out having seen it done in other places I guess, to whom I explain the reasons why I don't do it. Anyone who doesn't want to try on a lubricated open cell suit wet will have to buy it as-is, or leave it whatever they prefer.