That thing itself; refers specifically to a previously mentioned matter, focusing on that matter rather than other conditions or factors.
そのこと自体は問題ではないが、影響が心配だ。
That thing in itself is not a problem, but its effects are a concern.
そのこと自体は理解しているが、詳しい説明が欲しい。
I understand that itself, but I want a more detailed explanation.
そのこと自体を否定するつもりはない。
I do not intend to deny that itself.