The title is self-explanatory
There is a bug in the comments section that shows a code when submitting it.
Tell-tale signs of this bug is when a post is 5+ years old and the comments are also 5 plus years old.
Try commenting on the Corsair then you will find the error.
It is probably the SimplePlanes website HTML codes. It is possible that the code can't support really old comments and/or posts.
Correct me if I am wrong
The helix fossil's comments are broken because the devs locked it a while back and the web code to unlock it broke, so they kinda just ignored it because there's no reason to fix it