Re: You have it all wrong...

That is not quite correct. Damage/symptoms from viruses can be caused by a number of things, which includes:
- direct effects of the virus (e.g. lysing - exploding and killing - host cells)
- immunopathology (there are a LOT of ways the immune system can cause disease, since an active immune system can cause a lot of damage [that's what the immune system is there for! To kill nasty things that get inside of you! However, misdirected, or even healthy, immune responses can also damage host tissue]. For example, the cirrhosis in Hepatitis B virus is immune-mediated, and comes from various immune cells [cytotoxic lymphocytes, Natural Killer cells, to name a couple] killing the infected liver cells)
If the symptoms from a virus are caused by immunopathology, then a person with a weak immune system would still get infected, but might not suffer severe symptoms.
Most flus actually make those with weak immune systems (the old, the immunosuppressed, young children) much more sick and more likely to die (there are exceptions; the great "Spanish Influenza" generally killed the young and healthy, because the most severe symptoms resulted from immunopathology, kind of like SARS).
Only 50% of people with colds experience symptoms. There are many types of viruses that can cause colds, but rhinoviruses and coronaviruses are probably the most common. With rhinoviruses, symptom severity depends on the number of virus particles present. Since colds are fast-replicating, a person with a strong innate immune response (e.g. type I interferons, to protect uninfected cells and kill the virus in infected ones) is probably less likely to experience severe symptoms, because the virus will be kept at lower levels (or even eliminated) at an earlier stage.
I don't know of any evidence suggesting that a lack of cold or flu symptoms is indicative of a weak immune system. Specific antibodies (IgA) can protect from coronavirus infection (although they don't stick around very long, and cold viruses have a lot of subtypes with different antigens, so people do get reinfected) - a person who didn't get colds might just more protective antibodies than other people.
If there's any evidence that a lack of colds or flu indicate a weak immune system in most or all cases, I'd be interested to hear it. Tweet