LLC filing as a S-Corp is a corporation.  Therefore there are a few things wrong with mixing personal and business in one bank account. For one, the courts won't protect you if you personally get sued. Also legally if the money in the bank account is owned by corp, then you shouldn't be using it for personal expenses, as it's not your money. It's probably not illegal, but the IRS may decide it's income, and it will be subject to income tax and 15.3% self employment tax.   You should be on the payroll of the corporation, and drawing a reasonable salary, and paying withholding taxes, while the corp pays employer tax.  You have to declare assets on the tax return, so you definitely should not exclude any transactions.
The personal should be considered a shareholder's loan and it's probably a good idea to pay it back.
There are probably other concerns, and others may elaborate.