Unsupported / Weak Claims
**Weakness 2**:
`Projecting intermediate features to class space with a weight matrix from the last layer is not directly meaningful`
* Consider the output space of the network's last transformer block. Within this space, the weight matrix of last linear layer (operating on the outputs of that transformer block to project to class distribution space) represents class prototype embeddings. This is what the cited supporting work claims (and can be assumed true, for what matters here).
* However, in a different space, this assumption would not hold. For example, taking the last linear layer weight matrix of one network, and probing the outputs of different network (with common dimension outputs) will not give the same results. In the same way, although intermediate layers have a common dimension, these vectors lie in a different space.
* Claiming that projecting these vectors to class distribution space with a mismatched weight matrix results in low performance is therefore unfair. While the original vectors may not contain class information, it could also be that the weight matrix used is mismatched with the space in which these vectors lie.
* In the main rebuttal, when dismissing linear probing, the authors discuss possibility of spurious background correlations affecting linear probing, but there is no reason why the learned weight matrix of last layer would not be similar. In fact, even methods like CLIP have been shown to contain such spurious correlations. This actually raises a secondary issue of how correct (absence of spurious correlations) the final layer weight matrix is, to serve as good class prototypes. More importantly, the conflicting results of linear probing (whose theoretical weaknesses are all shared by the last-layer weights method), raise further concerns.
**Weakness 1**:
Given the weakness in above assumption, much of the proposed insights into network weights are rendered unsubstantiated. This leaves with minimal additional contributions over the existing works such as [10, 12].
**Final Response:**
I am quite aware about contemporary work in this topic and consider myself to have a decent understanding of those works. However, in light of highly positive comments by other reviewers, and given the chance that I may have misunderstood specifics of this paper, I will change my vote to Reject (as opposed to Strong Reject). I remain at Reject because the concerns discussed above have not been sufficiently addressed or discussed in the main paper or rebuttal. Further, most results figures and tables in the paper (and even rebuttal) still appear unclear (they are not described adequately and they are not self-explanatory either).