Often when I go the StackExchange Sig. Proc. web page I'll see a question listed near the top of the page indicating that the question was "modified one hour ago Community." Then I consider adding an answer or a comment to the question only to see that apparently the question, all comments, and all answers were posted four months ago! Is it a waste of my time to post a comment/answer to a question that apparently is four months old? (I must be misunderstanding something here
Rick, the Stack Exchange does that for posts that have either no answers or answers by no "ticked" answer. The idea is that we will eventually get answers to all questions. Our current site-wide answer rate is only 74%, which is not great for the *.SE network.
If you see one of these, and there is a sensible answer, please feel free to ping the OP (the question asker) to see if they need more information to select a "ticked" answer.
Just to clarify: a "ticked" answer is one that has an answer accepted by the original poster. If you look at the front page of DSP.SE, you'll see lots of questions, some of which have green around the answer box and some of which don't:
The ones without the green (with the white answer box) don't have an accepted answer:
In the ones with the green, the question asker has decided that that's the answer they were looking for and given a tick (and +15 rep) to the answerer:
My use of "tick" is probably British/Australian English: I mean "check mark". See the excruciating detail on the meta site for SO.