Okay. SO my thoughts about the whole Haku stuff with his mirrors being lightspeed....I actually don't think its an outlier. At least for Haku anyway.
Now the conscensus here about the whole thing in general being an outlier is because KM1 Naruto was "able to tag him" and Sasuke was able to perceive Haku through 1 tomoe Sharingan. Now It is clear that both things happened, thats no question. So why isn't this an outlier? From what I believe at least, the answer's simple: Haku wasn't light speed in either moment, but lower than it drasically.
And there are multiple points to this.
1.) If you guys remembered from the fight, it was confirmed by Haku himself that the Ice Mirror Jutsu requires and uses up an incredible amount of Chakra to be used for such a long period of time. That means the user must have a large chakra resevoir to even use the jutsu, and even with that, using it for a long time can drain them. In addition to this, Sasuke himself even suspects of this being true as he saysHaku's movements are slowing down as well for his chakra closing in on its limit (hence the "getting weaker" claim and the anime secondary canon supports this as Sasuke there flat out says his movements are slowing). In other words, the more Haku uses chakra for the jutsu, and the jutsu himself, the slower he becomes for using it over an extended period.
2.) According to this page, because Sasuke was familarizing with Haku's decreasing movements of speed, and was obviously on the brink of awakening the Sharingan, Sasuke's own speed was also increasing at the same time. This also supports this claim, otherwise Haku wouldnt have been required to target Naruto first to catch Sasuke off-guard instead of just attacking directly. And by "familarizing", it's not as great as you'd think. Sasuke needed minor instances, such as Haku repeling the water from his mirrors when moving , or his fireball jutsu interfering, to barely see glimpses of Haku's speed trails. Even then, there is a difference between perceiving speed and actually being able to match it with your body. Sasuke geting embarrased by Rock Lee is a perfect example.
3.) Regarding KM1 Naruto "tagging" Haku. If i remember correctly, the mirrors are what Haku explicity uses to even move at Light Speed or anything higher than his base speed correct? Otherwise the need for the mirrors would be completely irrelevant to how fast he moves. Well, if you take a look here , and look here , Naruto when using Kurama's power only grabbed Haku because he was out in the open, outisde the mirrors. Haku right before this states he needs to "quickly get to the next mirror". When he isn't using the mirrors, Haku cannot move at the speeds he'd normally travel at when using them. So Haku, when grabbed by Naruto, was never moving at the mirror speeds, and thats especially true when Haku's movements at this point have dropped considerably compared to near the beginning of the fight. Had Naruto never summoned Kurama's power in this moment, Haku would have still won handily, even with reduced power and speed.
4.) Last point from 3 brings me to this, a small thing to note out. Anyone ever consider the possibility of Haku being beaten by them at all big PIS? This occurence is a common kind of trope in fiction. The villain stomping the good guys, the good guys awaken a new power at the last second and start turning the tables. In this case, Sasuke awakening the sharingan at the last second and Naruto awakening Kurama's power at the last second. Haku and Zabuza needed to be beaten somehow, and given this was Team 7's first actual fight/mission that was notable, it would make sense for an ass-pull like this to happen so they could stop them.
5.) About the "getting teared to shreds" part. I believe Haku not being harmed by his own speed was because of stuff thats along the lines of being intangible or phasing through objects. We clearly see here that Haku is phasing through his ice mirrors when using them . Both the manga and anime canons confirm this. As such, if one were to be phasing or be intangible, it would logically support the fact that traveling at such speeds wouldnt harm them.
To sum things up here, besides PIS:
-Haku's speed gradually goes down if he uses the Ice Mirror jutsu for too long, at best giving him Lightspeed in the form of short bursts or short timespans, when his chakra levels are either full or nearly full. As such, this should not be an outlier for him.
-Sasuke, even with Sharingan, only ever perceived Haku when using small instances as mentioned, Haku being slower in speed for above reasons, and using the Sharingan's abilities to further increase his own speed capabilities, making it possible and more easier for Sasuke to keep up with Haku. That said, because of the speed difference between Light speed and where Team 7 was already, this would still be an outlier for Sasuke in the end.
-Naruto never tagged Haku when he was in Light-speed motion via the mirrors. Not only were Haku's speed and movements gradually decreased from before, but Haku was tagged by Naruto before he could use the mirrors to continue moving at speeds higher than his base speed. That said, like Sasuke, this would still be an outlier for Naruto as well.
-Haku not being torn or harmed by his own speed is covered by him having some level of phasing or intangibility thats demonstrated when he enters his ice mirrors.
So in the end, if no one sees issues with this, and this is acceptable, I think only Haku should be allowed to have this speed. It remains an outlier for Naruto and Sasuke, but Haku keeps it only in the form of short time-spans or short bursts, using the mirrors, when not on the brink of being depleted of power.