Looking at this comment thread, I noticed the times for the comments are missing:
When I reload the page, I see the times on the comments for a fraction of a second, and then they are gone. On shorter comment threads, I sometimes do see the comments. Initially I thought that they seemed to disappear if and only if the comments thread gets collapsed due to a large number of comments. When I click on "show 14 more comments", all comments are shown, including the times, but for shorter comment threads, I sometimes do, sometimes do not see them all; I cannot fully reproduce this.
Pale Moon version 28.1.0 on Linux (Ubuntu xenial 16.04), no user scripts.