I have noticed that if you purchase Militia Gear from the store, you are able to buy multiple copies of it, even though 1 piece of every Militia item is enough because they do not deplete once you have used them in battle, is this a glitch? or just some bit of miss typed coding? Just thought I'd let make a post about this.

also, you are able to restock this in the Dropsuit layout section, but here, unlike in the market, it costs you nothing. Thanks if you read this.

yes, and no.
If for instance you build two suits with militia modules, you really need one module per suit.

It's consistent with the EVE market behaviour. I suppose you're just not entirely aware of how the market behaves.
On the EVE market you can buy BPC's (BluePrint Copy), BPO's (BluePrint Original) or just plain equipment. The latter is a one-time-use item.
I think the behaviour we're seeing is a beta specific one. In EVE the difference between a BPC and BPO is basically the amount of times you can manufacture using them. BPO's are limitless (but cost a bloody fortune) and BPC's come with a limited amount of runs. Once those are exceeded they just disappear.
What we're dealing with in Dust (I hope it'll be this way for the beta only) are a form of instant-production BPO. What I mean by that is that they are BPO's that do not require you to actually go through the process of aquiring materials and production slots on a space station. They just "exist".