It is acceptable, yes.
In Australia, they actually tried to force people to vote for all the people that were running locally for the house of commons and for at least nine out of 10 on the senate ballot. That created a very complex system where political parties.... They got permission to refine the preferences. They introduced above-the-line voting, below-the-line voting, and in the end, the system came to an absurd...when small parties decided to unite their efforts, and if I'm not mistaken, the Australian Sports Party or the Motoring Enthusiast Party won a seat with 0.05% of the vote, or something like that.
Obviously, we should not go that far.
If someone believes that he only supports one independent, and he believes that all others are not trustworthy for some reason, he should be able to mark just one person.