gsa - as the discussion paper says - voters for any indyref 2 would be those living in Scotland at the time of the vote (regardless of where they were born). So any 'retired English' (how do you 'retire' from a nationality?) would have the same voting power as any other person living there. Given that everyone living in Scotland will from Apr 2017 pay the Scottish rates of income tax (so approx £300 per year more than if living in England and earning over £45k), it seems only fair that everyone directly affected gets the vote? Therefore also the reason to exclude all those born in Scotland and no longer resident there (so not paying taxes into the country).
As to 'go to lots of places and they are all retired English' - not sure where those places are? I live in an area where there are perhaps more English born scottish residents than many areas but we still have an SNP MSP and MP so it doesn't seem to have affected their elections...