Old questions, marked as recently modified, but no new content

Question

This one, for instance: ESP8266 Returns 'invalid' - Cause 4

Right now, Aug 7, 2016, 8:31am EST, the Top Questions page says this question was modified 7 hours ago. But the newest time stamp on the question's own page is 8 months old.

I often read old, bumped questions with "modified x hours ago" stamps in the Top Questions list, only to find nothing new.

I'm aware that an unanswered-question bot occasionally feeds the current-question queue, but it doesn't add anything to the question or its answers. Does up/down-voting bump the question? Voting doesn't add any to the content, either, or at least what it adds is minimal and qualitatively different from an edit, comment, or answer.

Or is it something recent that has been deleted? If there is no new content, listing it as having a recent update just adds noise to the Top Questions list.

Listing an old question isn't unreasonable in and of itself, but perhaps the "modified x hours ago" is being applied too liberally.

Update:

Where do you see this timestamp? That question seems to have fallen off the bottom of the page now, so let's take a more recent example:

On the Top Questions page at 160809,1322 UTC, this question's listing says "Modified 1 hour ago, Community". But on reading the question page, the most recent change I see is stamped May 11-th.

Answer 1

I got a response from one of the Stack Exchange staff:

For a very long time, we only had "modified" as a general "something touched this" indicator; no extra information on what. For even longer, we didn't actually keep a record that Community was bumping, so... All there was was "modified by no user".

This might change at some point, but only if/when we change how bumping works.

Answer 2

Does up/down-voting bump the question?

No, voting does not bump questions. Only answers and edits do.

Or is it something recent that has been deleted? If there is no new content, listing it as having a recent update just adds noise to the Top Questions list.

No, it is a tool to move question with too few visits and answers randomly to the top of the queue. A small detail: You are not ordering questions by newest or hottest, but by 'activity' (in your screenshot). Here is an excerpt from the FAQ:

• The Community user will bump non-negatively scored questions that have at least one answer scoring 0 and none scoring more than that.
  • Questions are picked randomly from the top-viewed inactive questions.
  • The number of unanswered questions bumped per hour depends on the site: 4 per hour on Stack Overflow, 1 per hour on Meta, and 2 per hour on Super User and Server Fault. The default for a new site is 1 per hour.

That should answer your question, as far as I understand it.