I often lead or am near the front in races. I really dont see that many problems with backmarkers who dont move over. It's happened to me a COUPLE of times in all the time i've raced LFS. It's happened to me in real racing too - infact i've broken ribs over a backmarker ignoring the blue before.
What I see an aweful lot more is fast guys who dont know what the blue flag means, who spam blue flag messages (I wish I could make that auto-kick! lol), and who are far too impatient in passing.
I do accept that mid race joiners can effect the leaders unfairly or unsportingly. A lot of things can happen when people are unsporting - that isnt a failure in the system, it's just because some people are ****s. Report them.
What I really would like to see the end of is the ignorance of people who spam off abuse to 'backmarkers' (who are often fast people who just joined or who just arent quite as fast in a long race or who have had an incident - rather than people who are outright slow) simply because they think the moment the other driver gets the blue flag message they should pull onto the grass or shift-s.
I've seen the discussion from some drivers, where somebody - and I find it gobsmacking - literally insisted that backmarkers should shift-s.
What should actually happen, is leaders should expect to loose time.
It's part of racing. If you dont want to deal with other cars then go and do rallying!
Personally I believe, that for the most part, backmarkers in LFS are far too forgiving of leaders because they are used to having abuse shouted at them.
I'm going to start insisting on a new standard for myself personally: I will not resist a leader lapping me and make it easy for them when their car is just about reaching my slipstream. I will no longer loose 3 seconds just because some 9 year old thinks he's God - purely because he did a do or die in Turn 1 and got lucky enough from his mayhem to find himself at the front.