With respect, a Parish Council is a planning consultee to the planning officer involved. Their comments can be, or at least should be, better versed on planning law than an individual resident who has less dealings with planning matters. They are also (or should be) representatives of the community as a whole and therefore able to assist a planning officer with balanced and unbiased general views of the community together with local knowledge, the detail of which borough planners can't always be expected to be aware of. Yes their comments are submitted in exactly the same way that all other resident's comments are submitted but they can often have more weight because of the above. Although I expect this may vary from borough to borough or even officer to officer, especially when an application is dealt with under delegated powers.