それ自体はおめでたいことですが、１つ気になるコメントがありました。

、。

The thing itself is a cause for celebration, but there was one comment that caught my attention.

Literal

That itself [topic-は] auspicious thing [copula-ですが], 1 concerning comment [subj-が] existed [polite-ました].

それ自体 '(the thing) itself / X itself' is the stock reflexive phrase for isolating the subject from its context. おめでたい 'auspicious / congratulation-worthy / happy' is the formal/elevated form of めでたい, with the honorific prefix お. 気になる here appears in its attributive form as a relative clause modifying コメント 'comment' — 'a comment that catches one's attention.' Neatly shows how 気になる can modify nouns directly.