This may sound obvious, but it's interesting to realise that many of the things that people with dementia do, and which sometimes attract comment, are things that people who don't have dementia also do.
Two recent examples that I've come across online:
Someone noted that their husband cried when moved by music. This is very common. In fact, I would think that most people at one time or another have experienced this themselves. In the case of a person with dementia it could be considered something worthy of celebration that this happens, as people with dementia can become apathetic and fail to respond to most external stimuli.
It's well known that many people with dementia talk to themselves and/or make noises when, for example, they are trying to concentrate on something. So do many, if not most, other people. Admittedly, people without dementia often talk to themselves silently but it's not uncommon for them to do this aloud.