If I am wrong in writing or understanding the text I apologize, since I am not a native English speaker I do not have your competence in the English language. I still apologize for any misunderstandings or if in my writing I convey a wrong impression.
your point of view is a possibility, but you must recognize that my point of view is also, I do not say that yours is wrong, I only say that we cannot be sure of it, I just try to keep the mind open in the absence of descriptions precise canons.
Both for the comparison with the city and for the comparison with the moon, in my opinion both our assumptions could be true, because neither of us has canon support evidence, I don't try to say that I'm right, I'm just looking for to say that both of our hypotheses could be plausible.
For the two Gloriana classes and the Abyss I read this quote on wikia: "The Blessed woman easily eclipsed the Glorian-class battleships used as flagships by most other space naval legions."
https://warhammer40k.fandom.com/wiki/Ab ... Battleship
Maybe it's me that I didn't understand the meaning, but from the sentence I understand that they weren't on the same side, but if you read the book and say they were on the same side then I trust what you say.
As for the attack on the planet Macregge, I read either that an attack would have been a suicide, that the Abyss class was able to withstand the fire of weapons in defense of Macragge, is a bit of a contradiction.
As for the Cestus fleet we are talking about six ships, in my opinion they are many, you say that it can be threatened by lower class ships, but 6 ships have not even made a scratch and they have been destroyed quickly.
To summarize the meaning of my speech, what I am arguing is that it is wrong to say that the Abyss class is a normal ship, which could be put in difficulty by normal ships. A Glorian-class ship is described as capable of exterminating entire fleets on its own, an Abyss-class ship is described as much more powerful. This is why I say this.
In fact, to break down his shields, as I wrote earlier, they use a defense platform, two orbital attack systems, warships, and a suicide attack by a battleship, and they had to bomb for a whole hour. And all this breaks down the shields, I quote the quote: "The size and scale of the ships have made all the countermeasures obsolete. For the first hour, nothing could pierce their Void Shields. Nothing even managed to scratch the skin. it took the combined firepower of a battle station, two orbital defense platforms and a suicide attack from an imperial warship to finally penetrate the blessed Madam shields. "
https://warhammer40k.fandom.com/wiki/Ab ... Battleship Let's talk about a non-naval firepower, but for planetary defense, which other ship would have been able to sustain so much?
How can we say that other lower class ships could be a threat if they have endured all this for an hour?
While for the Furious Abyss instead they had to resort to internal sabotage because the weapons of the other ships were completely useless against his shields. Cit: "These wounds were a simple puncture for a huge beast like the Abyss-class warship, and the Word Bearers ship responded with a devastating save."
https://warhammer40k.fandom.com/wiki/Furious_Abyss
If I have reported any data incorrectly, I ask you to please let me know and apologize, it is not my intention, I am here to learn, certainly not to teach.