Performance is a feature, or at least it should be, of any good design. Of course it might be a very low priority feature, so it would be valid to close any is

Performance is a feature, or at least it should be, of any good design. Of course it might be a very low priority feature, so it would be valid to close any issue reports as "WONTFIX" if the devs have no time or feel they are better spending their time on other matters, especially if people on slow connections are not expected to be a significant part of the target audience, but commenting on potential performance issues is perfectly valid when discussing a site (re)design IMO.