Typically a moderator will lock a post for one of a few reasons:
A question or answer where repeated voting or editing is happening in a way which attempts to game, hack, or otherwise abuse the system.
A question that gets opened and closed repeatedly many times without achieving community consensus on whether it should stay open or closed.
A question that, for whatever reason, continues to attract flame posts, spam, or other inappropriate answers.
A question that is repeatedly vandalized by its asker; for example, to drastically alter the meaning of the question that invalidates existing answers, or to obliterate/obscure the question.
See What is a "locked" post?
I locked the post temporarily because it was closed as a duplicate by community consensus, then started to receive flags disputing that it was in fact not a duplicate of the following question....
Is commented out code really always bad?
I felt as if I agreed with this, however it had over 10 answers already and at the other over 13. I couldn't really see too much else of value being added in addition to what others have already answered well and completely. I was hoping that with a temporary lock that it wouldn't attract anymore answers and if anybody was concerned or highly disagreed with my reopen of the question then they would bring the subject up on Meta for us to discuss.
I am glad that you brought it up because this question can be the perfect vehicle for such a discussion.