Banning Multiple Accounts-few suggestions

Before 3 months I was unfairly banned from DP for having multiple accounts.

But the problem is I did n't have any multiple accounts at DP ..

I have a few points to suggest to Mods for banning Multiple accounts
a)First IP address (same IP being used by multiple accounts)
b)Before banning a member they should also check whether the other member has taken part in the discussion created by banned member and due to this whether banned member has some advantage

Case 1:-right
In a sales thread ,member1 lists a link for sale ,member 2 (using the same ip takes part in the thread) in this case
member has to be banned


Case 2:-wrong
Mods find out two members using the same IP and ban two of them..
In this scenario if a member logins from office/working place this scenario may happen very often.
Because large organizations do n't have a single IP for every single PC.they have single external IP for about 300 odd PC's

I hope Mods would look into this and some common sense would prevail before banning members considering these scenarios