So once again I guess the take away point here is - don't do something you're not trained and competent in, otherwise try and do the basics to the best of your ability (plasters, reassurance, get help, get out of the way).
People should absolutely have the confidence to crack on with chest compressions without formal training, similarly, maintaining an airway. With an unresponsive casualty, to stand by due to a lack of confidence may hasten their death/increase the likelihood that they end up with severe brain injury through oxygen starvation. To have a go and do you best
may just mean that they are in a state that when professional/qualified/equipped care turns up, they can do something useful.
Of course the gold standard is to get some training, and frankly i find it astonishing how few people do - especially when the overwhelming likelihood is that it is a family member or a good mate that is the person in desperate need for first aid from you.
Re. one the the above points - agree that motorcycle helmets should be removed - but only if essential to perform immediately necessary first aid - e.g. to maintain an airway and/or to perform CPR. In the example above, if the person is still talking then it wouldn't be necessary to remove the helmet. There is a correct way to do so in order to minimise neck/spinal movement.
The trick is to work down the priorities of first aid - Airway, Breathing, Circulation (yes i know its more nuanced than that, but for the purpose of this thread...!) i.e. - if the airway is blocked - you MUST do something about it (i.e. clear it, get the casualty into a position where it is cleared and unobstructed). If they are not breathing/oxygenated blood getting to the brain you MUST do something about it (i.e. chest compressions + mouth to mouth if you are comfortable/able). If there is a catastrophic (i.e. arterial) bleed, you MUST do something about it (i.e. direct or indirect compression). There are right and wrong ways of going about these actions, as well as ways which would minimise the likelihood for causing secondary long term complications/injuries, but everyone must still have a go after first calling for help - unless there is someone better able with you that can perform those immediate actions more effectively.
Example, a motorcyclist is unconscious and unresponsive. After ascertaining this, you remove his helmet in order to open up his airway and perform CPR. In the process, it later turns out that you have exacerbated a spinal injury and the person is paralysed. He is, however, alive and with a functioning mental state - you having maintained a supply of oxygenated blood to his brain until the ambulance arrived equipped with a defib etc. The alternative scenario, you look on, paralysed into inaction as you are concerned about something you read on the internet about never removing a motorcyclists helmet/a nonsense sticker on the helmet itself stating the same thing; the person is pronounced dead at the scene when medical care does turn up, and you spend the rest of your life wondering whether you could have made a difference for that bloke and his family!
Appreciate that this is all a little emotive and heavy a subject, but i do think it is rather important. Perfect excuse for people to book themselves onto a first aid course/get your workplace to do so at their expense!