Summary:
Whilst having a flint and steel in your hand and mining a block, the durability on the flint and steel goes down without using the item to light a fire. If this is intentional than disregard this message, however, this does seem to be the only tool that has only a right-click function to lose durability.

Steps to Reproduce:

1. Obtain a flint and steel
2. Switch to Survival mode
3. Break a block with the flint and steel

Observed Results:
The flint and steel loses durability.

Expected Results:
The flint and steel should not lose durability.