Learn Portuguese (Portugal): Se tu coças assim, o teu braço vai inchar. - If you scratch like that, your arm is going to swell.

While se (if) often triggers the future subjunctive for hypothetical future events, we use the present indicative (coças) when referring to an action happening right now or a general truth. Since the person is currently scratching, the present tense fits perfectly.

How could we incorporate fartar-se de to emphasize that the person is scratching excessively?

You could change the first half to: Se te fartas de coçar assim... The expression fartar-se de followed by an infinitive is used to describe doing an action a lot or to excess. In this context, it translates nicely to 'If you scratch yourself so much like that...'

Is it common to drop the reflexive pronoun and say coças instead of te coças?

Yes, in casual spoken Portuguese. Technically, coçar-se means to scratch oneself, while the non-reflexive coçar usually takes a direct object (like explicitly saying coças o braço). However, in everyday speech, people often drop the pronoun when the context makes it completely obvious.

Why does this sentence use o teu braço instead of just saying o braço?