If someone wants to find the full passing solutions, they are all over the internet already. The objective of FreeCodeCamp is to teach coding, not awarding certificates. It doesn’t matters, really.
And as said, unvoted or downvoted comments could be periodically removed by the system.
If you ever saw this feature implemented somewhere else, you’ll know how powerful it is to broaden the subject and give valuable insight the the same code usage in other situations not foreseen by those that assembled the lesson.
The community eyes can always see farther then any pre-assembled team. Well, a goal–oriented and united community such we campers, that is it.