Do the majority of infections clear completely?

The numbers are still unclear. Keep in mind that HIV/AIDS, TB et al have had a much longer time around to be studied. The researcher I quoted above mentioned studying HIV for 20 years. COVID is only approaching the end of year 5. In spite of its recency, we do still have a wealth of data to tell us how threatening it is, anyway. Being re-infected several times per year is certainly not tipping the odds in anyone’s favor, either.

The safest thing to do is also, thankfully, the simplest: wearing a well-fitting, N95-grade respirator whenever one is away from their home. These types of respirators are, regardless of anything you may have heard, extremely effective at protecting you and others from infecting one another, even if no one else feels so inclined.