A smart group is a result of a search. The contacts in the group change dynamically depending on the criteria.
Though, I have several use cases where i want to be able to force some contacts in the group even if they don't meet the criteria in the search. For example, i want to send a newsletter to people that subscribe but also automatically to members.
It seems to be possible to manually add some people to a smart group like if it were a standard group. But is it a good practice ? Is there any known caveat ?