Alright, I decided to read through the speed thread because it's actually not that long and I'm also putting off real work I should be doing.
All I can say is that you obviously mean well, and have put clear thought and effort into your explanation, but it will unfortunately never be accepted on this site. The main reason for this is because your entire argument for Sting's attacks being lightspeed is simply founded on an incredibly shaky premise.
For starters, the laser argument: Keep in mind that fiction authors generally misuse the hell out of the physics of certain tropes, with lasers being one of the most prevalent examples, in simple attempts to advance their story or show off one characters abilities without taking into account how their real life counterparts actually function (Another example of this is black holes, which are
rarely portrayed as realistic, if ever.). It is because these tropes are so frequently misused accross a variety of fictional franchises that we don't just give them the benefit of the doubt anymore, and they have to prove, through consistent showings or verbal explanations, that they are the real thing. Sting's laser, while it could be pure light, does neither of these. All the story does is exclaim that it's "A laser?" and nothing else.
The case is similar with Erza's analysis of the attack being "Light" (which is actually refering to
this attack and not the laser attack). There's no further hint
at all that would give the impression that Sting's Holy Ray attack, or any of his attacks, are lightspeed. Yes, I'm aware, "Ray=Light, isn't it obvious?" Just refer to what I said earlier about authors misusing real life phenomena in many fictional mediums without much thought about what they are actually prescribing. Speed feats are the most strictly judged of cases like this, especially cases involving of Light, Lightning, Lasers, etc., due to how much they are misused and misattributed.
Moving on to your counter arguments. Most people don't do these, so I personally appreciated the fact that you had them, but they fall short, and are contradictory to boot.
Your first counter argument, you mention how Sting's light is real light since other characters have shown that their magic exhibits the real life properties of whatever element they are manipulating, like Laxus' lightning, for example, displaying the attributes of real electricity. This was easily your best point. However, it falls apart when we see that Sting's light doesn't act like real light (I know, you have a counterpoint for this too which I will address in a moment). His light bends with no external source of gravity to bend it, and, most importantly, it physically interacts with people and objects, and creates things like explosions and seriously bruises people he uses it on, both of which normal light does not do. Light of higher frequencies and shorter wavelengths (X-Ray, Gamma, etc.) can kill people, but it does not create explosions n' shit, and seeing as Sting's "light" is clearly visible light since we can see it, this is automatically ruled out from the start. Now, the only other time light can physically harm you is if it is focused into something like a laser. Funny enough, Sting does have what was described as a "laser" as you already know, but again, it is very questionable due to authors sucking and the fact that only one of his attacks is described as a "laser" and other ones, like
this for example, are not and are indefensible. Essentially from what I can see, his light doesn't hold similarity to actual light, which is exactly what I said earlier in regards to the laser shenanigans.
Now of course, this is fiction, and you at least acknowledge this and mention how
"it's magic" and that it doesn't need to follow the rules of real physics. But, if that is the case,
then WHY have an enitre counter point to the claim that "his light isn't real light" by using Laxus' lightning as an example of magic having realistic properties??? It's a complete 180 from what you were just talking about further up. Also, rogue mentioning how light "bends to his whim" is more than likely just him phrasing it as "it does what he says" since he can literally control it, and not because of a gravitational source. It's also generally important to note, we do count Laxus' lightning as real lightning partially for those scans you provided. Meaning his attacks move at lightning speed. So why then would people massively stronger and faster than sting that Laxus has faced fall victim to being struck by his attacks when they should supposedly be faster than Natsu who was in turn faster than Sting's "lightspeed" attacks? Either it's massive PIS and Sting's attacks are lightspeed, or Sting isn't lightspeed and Laxus' lightning still holds the best basis to judge the different character's speeds (which is admittedly very impressive on it's own, especially by HST standards.).
Point in case:
1. Authors suck and don't know real life, and Fairy Tail does an insufficient job showing that it is an exception to the rule.
2. Your whole premise is lacking overall and needs a sturdier foundation (The Erza argument actually wasn't half bad, but it wasn't enough to disprove the above point.).
3. Sting's light doesn't act like real light, and using the excuse that "it's fiction" merely contradicts part of your own reasoning (which further exemplifies point 1).
4. I'm exhausted so I may have missed something, but this is just my 2 cents on reading the thread, so good job.
. I would like to know what other reasoning is ridiculous? Im sure we can debate about it. 
