The PhabricatorAuditInlineComment class is implementing PhabricatorInlineCommentInterface interface, which tells, that it supports synthetic authors (e.g. ones, that are used in Diffusion for showing lint messages in form of inline comments). However the getMarkupFieldKey method is generating markup key based on inline comment id, which is absent in case if comment is added by synthetic author. At the end all inline comments from synthetic author are rendered with same content (because markup field key is the same).
I recommend changing
public function getMarkupFieldKey($field) {
return 'AI:'.$this->getID();
}to
public function getMarkupFieldKey($field) {
// We can't use ID because synthetic comments don't have it.
return 'AI:'.PhabricatorHash::digest($this->getContent());
}As it is done for Differential Diff Inline Comments.