This wouldnt be breaking the rule in any way no matter who attaked who in the second fight. A is allowed to attack B with any of his characters wheneve he likes, as long as its not Bs 10 minute system leaving grace period. Thats the benefit of winning.
I addition when you die you are only restricted from attacking the CHARACTER that killed you, not the player. B could attack C, because it was A that killed him, even though they belong to the same player. In this case it doesnt matter cos C attacked B, so its double OK.
TL;DR: No. Did A die? No. Then 5.8 doesnt apply to him.
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