Or someone who is actually a programmer could come in and tell you that sucks.

That sucks.

But seriously game programming (and especially multiplayer) doesn't do things synchronously like that - because it is incredibly slow. We try to limit IF statements as much as possible because every check is costly and the code has to run these checks every frame - not just once at startup.

If I were to guess the guardian shield is currently a part of the regular shield class (talking about object oriented classes here) - OOO would have to separate the guardian shield completely out by either duplicating the class or subclassing the current shield. Then they would have to program the shield to not take ticks (possibly taking snippets from trojan shield mechanics if compatible) - this would then have to be tested thoroughly because it is a "major" mechanic change that could mess up the shield taking damage from legitimate sources. Then they would have to go through the LD code and make sure all references to the guardian shield points to the new class (class switching, player spawning, etc...)

that's it

Alchemer charges always did that, even with the invincibility frames. I like to call it the hypercrit. If you glitch a charge into a target, the rebounds are instantaneous and all hit before the invincibility frames kick in.
Also, contrary to popular opinion, I use a style that makes AA very much useful as a gunner. It's closer range so you can dodge quicker and land shots with better accuracy. It can be risky, so it takes some practise, but it can pay off. Also, if you're leading your shots, you usually end up firing at a larger angle than AA can pick up anyway. It's really only at a hinderance at mid range on a target that's circling you, but there's the AA toggle button for that.

Read the part where it says I'm not a programmer and that someone who is would obviously be able to come up with a more elegant solution. The point was to illustrate that it is conceptually nowhere near as "impossible" as someone had postulated. If someone who isn't a programmer and has only taken intro comp sci courses can produce a solution, then obviously a professional would be able to produce a much more optimized one. But good on you for not letting the point go by you.

Yes Griseolar it is elementary, since in the field, it is amongst the first things you learn as rudiments and anything I know about programming is elementary since I'm a noob at it. I didn't say it was general knowledge, I said it was elementary. If you want to debate semantics, there are better places to do that. I've already made my point that it does not require this bug to fix your little issue with how mist bombs interact with guardian shields.

Seriously, it shouldn't exist in the first place.

I understand why it does. It makes Lockdown more fair and that's understandable in most cases, but then again, it takes away realism. One thing I hate about invincibility frames is the fact that I'm unable to attack someone if someone else is using their Setenza/Argent Peacemaker, leaving me open for damage. Remove that, and there would be no problems. It would be more realistic as every hit you do, you know it will land damage.

It introduced a new line of gameplay, and made other weapons usable such as the Hammer, Autogun line and Cutter line.

I'm not going to go into much detail over this as other users has already done so, but what I am going to say is that I liked the bug. It was great, and made Lockdown more enjoyable for all.

I say, bring it back as a feature!