From basic principles and texts:
God Himself is unknowable; He only makes Himself known through His attributes (qualities) namely He "emitted" the ten Sefirot and everything else and by them He is knowable to man. It is He that fills the Sefirot [and they do not fill or constitute Him] Patach Eliyahu.
Sefer Yetzira Perek 1 Mishnah 5:
עשר ספירות בלי מה מדתן עשר שאין להם סוף עומק ראשית ועומק אחרית עומק
טוב ועומק רע ... אדון יחיד אל מלך נאמן מושל בכולם ממעון קדשו ועד עדי
Ten Sefirot "of What," their quality is Ten that's infinite. A depth
of first, a depth of last (Chokhmah-Binah) A depth of good, a depth of
evil (Keter-Malkhut) A depth of (south, north, east, up, down, west)
the singular Lord Almighty, the faithful King, rules over all of them
from His holy dwelling place for ever and ever.
Keter is known as the axis of Good as the commentators bring, as per (Ps. 73:28) ואני קרבת אלהים לי טוב / As for me, drawing nigh to God is what's good. So its "antipole" Malkhut (and which has nothing of its own but rather is the summation of all ten) is known as the dimension of Evil as in distance from God, that is, "as it were;" i.e. if it were possible, that's the illusion of the world, etc.
So, analyzing the statement you're asking about:
- "evil" as a "quality of God" - Yes, per #1 and 2, insofar as it's a quality of His manifestations particularly the Sefira Malkhut, and the illusion of the world as separate from Him.
- asserting that negativity enters into the essence of the
Absolute. - No, nothing enters into His very own essence, for His
absolute essence is unknowable as per #1 and furthermore it is He that fills the Sefirot and not vice-versa and similarly from #2 it is He that rules them and not vice-versa.