How much bleeding with a UTI is acceptable?

Small amounts. In some cases a UTI will cause an irritation of the lining of the bladder. This is called hemorrhagic cystitis. This can cause some blood in the urine. In most cases it is not a lot but it can be alarming. This should clear within a week of being treated for the uti. If you have continued bleeding after the infection is cleared then you need a follow up appointment with your doctor.
A little. A little blood in toilet bowl can be quite impressive, but, you can see through it. Blood should clear up within 24 - 36 hours of starting appropriate antibiotics. You can not see through urine when there is a large or significant amount of blood in the urine.