1- At the very beginning the authors claim that simplified models are not self-consistent. It would be good to argue more specifically that they are constructed at tree level and are not a well-defined quantum field theory. From that perspective I also disagree with the bottom-up and top-down argument, because even bottom0up Lagrangians need to be quantized.
2- In the introduction on p.2 the authors motivate a certain class of models. Now, at least almost all models suggested by theorists will eventually be proven wrong, so it would be good to argue that this paper is not about an interesting model but about showing the absurdity of simplified models.
3- I am missing a little bit more of a structure in the discussion of the model starting on p.3. It might be helpful to give a graphic representation of a couple of sample spectra.
4- On p.5, why is an additional U(1) symmetry a reason to ignore Majorana
5- On p.6, could the authors please comment on scalar mixing beyond tree
level? What happens to the analysis if we allow for a small mixing?
6- Why is it reasonable to assume zero kinetic mixing at some high scale? I would agree with such an argument if the model had a GUT-like motivation, but this argument is never given before. For the running of the mixing, what are the assumptions of the new particle masses/thresholds?
7- Before going into Sec. 3.1 it would be nice to mention that the authors consider the relic density a constraining factor. I agree with this approach, but some of our colleagues consider this an unjustified relic density fetish.
8- On p.8, I am not sure every reader is familiar with the procedure applied in Ref.[64,65], please be more specific.
9- I am not sure I understand the argument concerning the chi-chi mixing, especially how strongly we can argue that the mixing remains small even for equal masses.
10- Still on p.10, given the relevance of W and Z funnels in the co-annihilation, are the Feynman diagrams in Fig.3 really the ones the authors would like to show?
11- Starting on p.12 please add a few Feynman diagrams with the relevant LHC processes, including the new particles, etc. As it stands it is very hard to get a grip on the different LHC constraints (which I have no doubt are correctly computed).
12- For a quantitative discussion of electroweakino pair production in supersymmetric models it might be helpful to look into our recent paper on exactly this topic (I am not aware of other focused studies of this topic). At least older readers would appreciate some more
analogies with the established supersymmetric models.
13- Sorry, but I am not sure I understand the argument on p.13 as to why the analysis is conservative, even in the presence of (neglected) systematic and theory uncertainties.
14- On p.14, where do these benchmark points come from and what kind of patterns are they expected to represent? Where do they stand in terms of non-LHC constraints? And why are the three first benchmark points most sensitive to the same analysis looking for soft OS-leptons? The fact that these leptons are soft suggests a link to small mass splittings?
15- At the end, the paper seems to end without making an explicit point of the funny bottom line. And what would remain of this bottom line when we loosen the relic density constraint? Would a too small relic density have an effect on the most relevant LHC searches?
16- There are a few minor language problems/typos, please read the paper once more carefully.
17- I know it is a pain, but the reference list misses a lot of relevant references on anomalies related to Z' searches.
18- Please update the references with the journal numbers. Actually, I only care about the SciPost references, for example our Ref..