[Icyphox]

Yeah, this one does. Some others on the frontpage don't. Interesting.

If I were to hazard a guess -- it looks like a templating bug. Some template has a period in it.

[OJFord]

Except that this one does on the front page too, so it's not like 'front.template' has no full stop and 'submission.template' does.

Similarly in 'threads' some comments do and others don't. 'tis mildly curious.

Edit: I went back to front, and this submission now doesn't have it. :shrug:

[jeroenhd]

Looks like jn6118 figured it out[1]; the dot seems to indicate that the comment is that user's latest post.

[1]: https://news.ycombinator.com/item?id=25197967