The Edelrid Micro O wiregate accessory carabiner is popular with tree climbers. The Micro O has a break strength of 150kg so it's definitely more than a $2 Shop special but they will break when configured inappropriately.The broken Micro O below was used to attach a foot loop to a hand ascender. In this configuration the carabiner is not expected to provide life support - a break means a sudden shock load on your leg and some inconvenience mid-ascent… but that's it.
When configuring your system, simply apply a 10:1 safety factor on all connector placements. A 10:1 SF would mean the Micro O can be used in a situation where less than 15kg of load is to be applied (150kg break strength divided by 10).
The foot loop connector on the hand ascender has your entire body weight applied to the weakest link through the foot loop when you stand on it, in this instance the Micro O - a force far greater than 15kg.
Another issue with the Micro O as the foot loop/hand ascender link is the metal-on-metal connection point between the carabiner and the bottom hole of the hand ascender - the wear is significant on the Micro O bar (see bottom left).
You only have to hold the Micro O in your hand and you'll know in your heart it is not designed for this application - loosely translated, common sense must prevail, please don't ask for your money back!