This page is a curiosity. Ironically, I think the removal of the picture makes the article seem more competent, as it would lead one to believe that the physical traits of the anomaly were developed from imagination rather than taken from an (obviously drawn) image.
To its credit, the anomalous qualities are rather unique. The auditory effect can only be likened to a less interesting boring version of RPC-042. The transforming fur is something I haven't seen before… it's admittedly kind of comical. I believe this is what SCP members would disparagingly refer to as a "monster manual" entry: someone's badass idea described in meticulous detail, presumably for others to marvel at. On the plus side, the anomaly is remarkably memorable (maybe I'm just biased towards cool dinosaurs), and the article feels engaged with the creature. However, that's basically it for the positives.
The writing is of a laughably strange sort. The conprots aren't particularly egregious, but the description kicks off with the miscapitalized and wildly indecisive "RPC-151-ARC Is a vaguely bird-like, flying mammal creature." There are also crazy run-ons and a few words flat-out missing. Oddly, it's still not the worst experience I've had reading a published RPC. It's otherwise the standard type of inconsistent and unpolished writing that oddly characterizes the early days of both SCP and RPC.
Experiment 151-1 is absurdly stupid. I thought I had to be misinterpreting the test somehow, but it seems the goal was to have one guy anger the monster and have another guy try to stop it with his bare hands. Are they doing science or recording some kind of home movie? Judging by context, they were testing its strength, but it's not hard to envision a more intelligent and rigorous experiment. Even by summer 2018 standards, this is wasteful of CSD assets. That, strangely, is how it ends. There's no real conclusion.
I don't need to convince anyone that this article is good or bad, but it's the circumstances of archival that keep it in memory. As much as I've taken cues from good articles, I've also read "bad" articles that stuck with me. They may have had good pieces to pull out, or they may have unintentionally taught through bad example. Regardless, these articles had their own place in history and their own value. Upholding quality standards is our highest priority, but isn't it a shame these articles will all someday be erased? Most won't be remembered or archived in an accessible way. Our history, too, is written by the winners. We have an immense library, but it's strange when we find ourselves burning it.
Above all this, 151-ARC is immortal. It's the "bad article" that will be forever displayed for all it has to offer. 2/5 for cool dinosaur. Hey, it's not as if the score matters anyway.