since you can't cure cancer
Yes you can
Inexperienced mappers will leave feedback pointing out sightlines without any regard to if they are a good sightline or not. It's one of the most common fallacies of this community, because sightlines are easy to point out, determining if they are good or not is not.
Understand that sniper is a class, like the other 8, that must be balanced in your map. This means not only removing places they are too strong, but also leaving in places where they can perform their role. For the same reason you have hiding spots for spy, cover for heavies, perch points for soldier, chokes for demomen and pyros, you want sightlines for snipers.
I recommend that you do not take the fact that people are commenting on your sightline as a bad thing, rather when you are playing your map or watching a demo, study the area and figure out if a single sniper is gaining too much power from it - this usually happens when players have no other choice but to enter his range of sight with little cover. Long sightlines can be fine if they have alternate routes, for example.