I welcome the effort to present the description of the current version of neXtSIM, but I think the paper needs to be improved in several directions before I can recommend it. 

1. I miss a good description of the numerical part of the model, in particular its time stepping, details of the spatial discretization and the general workflow. The authors cite their previous work where I guess some explanation can be found. However, the value of technical papers in GMD is precisely that they provide an opportunity to document the model and describe details that would enable others to learn and to follow. Many quantities are left undefined in section 2. For example, the stress tensor appears in (1), and on line 54, but then disappears. Instead, there are undefined components, and finally there is the \sigma but without the boldface. Please be precise, it is almost impossible for a general reader to follow. The quantity K (bold face) is not defined, and \eta appears as sea surface height in (1), then as viscosity in (3), and \eta_0 is not specified. This continues in section 2.2, there are undefined strain rate invariants, the parameters e and P* are not specified, the equation for velocity is written (17), but no discrete equation for the stresses, and the reader is referred to other papers for \alpha, \beta and \beta' and \tau.  

2. The presentation of section 3.1 should also be improved, and the iterative procedure for the drag coefficients needs to be presented in more detail. 

3. The explanation in section 4.2 needs a figure showing (defining) the geometry of the procedure. 

4. Many technical steps in the model are related to the decision to use a moving mesh. First, it would be worthwhile to discuss why this choice is necessary and compare it with other possibilities. Remeshing should be equivalent to some diffusion, and if the choice made by the authors is motivated by the desire to keep the damage fields localized, the question is whether a comparable result can be achieved by using a high-order advection scheme. This would simplify many things (but make the advection more complicated). Second, I do not see any discussion of how mesh deformation will affect vector and tensorial quantities.

5. In the discussion of the test case (section 5.1) the authors compare the performance of two damage update schemes. While the field in 2c contains more detail, it is a discrete implementation and grid-scale details cannot be interpreted reliably. I would be suspicious of any features that are the size of several grid cells. Similarly, Fig. 3a and c show that there is grid-scale noise in normal stresses where damage tends to 1, meaning that the stresses are not really differentiable. Please, include discussion of these issues. From a numerical point of view, I would be concerned about the appearance of noise in solutions and consider some measures that restore smoothness.  

6. I also miss some general discussion of how the BBM and EVP compare with each other in both the simulated sea ice state and the requirements on time step and computational expenses. This would help the reader to see the differences and decide where the BBM rheology leads to advantages. 

Minor points:

3,4 'but fails ...' But should it? At these resolutions the scales where truncation errors are small are perhaps 25 km or larger, and these scales are already too large for most leads.

7,8 'independently of resolution'? Why one needs leads and ridges if a mesh is coarse? Do they correspond to any physical reality?

11 'give insights ...' This is what I do not really see

Introduction gives emphasis on historical aspect, and the time intervals of simulations that are mentioned there are discouraging (ten days, an entire year...). I would not not mention this, as it only tells that the model was not really ready.

64 'on any' ? 

68 'In it'  What is it?

74 cascade Marsan

95 P_max is very similar to the sea ice strength in Hibler's rheology, do you select similar parameters as in (16)? Please specify 

119 (P0) and (P1) should be explained. Also it should be explained how derivatives are computed, and there are other things, see 

145 Why n+1 in the absolute value |u_w-u^{n+1}|? I hope a linearized version is used.

147 'donates'?

156 stress tensor was boldface initially, please be consistent, there are several places before

168 'particularly after'  It would be better to cite some examples. 

formula (22) C? it was Ch and Cm before

406 10^5 seems to be rather limiting, a 1/12 degree mesh has already much more cells in the Arctic.

468 'Some loss ...' Can it be quantified?

481 'This sampling ...' Why this sentence is needed?

527 'Such rapid change ....' See my point 5.

Fig. 2, caption, 100 by 100? (It is 1000 by 1000 in the text).

Also add an explanation for b and c.

 

Fig. 3, caption, why a,c,e  and b,d,f are grouped together? Please arrange consistently. Also in the text (line 508, a and f?).