Sources
Agreement with the author/source
As XXX perceptively/insightfully states, I ...
As XXX correctly notes, I ...
As XXX rightly observes, this is ...
As XXX appropriately points out, YYY is/seems to be ZZZ (adjective/noun).
I/we rather/somewhat/strongly agree with/support (the idea that) XXX.
XXX provides/lends support to YYY's argument/claim/conclusion that ZZZ.
Disagreement with the author/source
I/we rather/somewhat/strongly disagree with XXX/ that YYY.
As XXX states (somewhat) undearly/erroneously, ...
XXX does not support YYY's argument/claim/conclusion about ZZZ/that ZZZ.
Although XXX contends that YYY, I/we believe that ZZZ.
However, it remains unclear whether ...
It would (thus) be of interest to learn more about YYY/how ...