Just wanted to pass this along - have never experienced this myself before. I app'ed Discover Miles for the 6mths and 0% 6mth APR. They approved. Upon approval they send me a letter saying that if I sent a W-2, pay-stub or tax return to verify my income, they may increase my CL. I sent the paystub one week ago. I checked back today a they had nearly doubled the original CL which was generous to begin with.
Guess I am saying maybe sending proof of income can help with CL increases - particularly if income has gone up.