To Clear or not to clear ARM Cortex-M NVIC interrupt pending

No, you don't need to clear the pending status in the NVIC, that is done automatically when the interrupt is serviced (see Joseph Yiu, The Definitive Guide to ARM Cortex-M3 and Cortex-M4 Processors, 3rd Edition, page 247).

However, you may need to clear the condition causing the interrupt on the specific peripheral.