No, there has not been a recent change in Community algorithms. You will see its name on the front page of the site in the following cases:
- It "bumped" a post to give more visibility to overlooked answers.
- Suggested edit by an anonymous visitor was approved; such edits are attributed to Community because there is nobody else to attribute them to.
- A question was bumped by a spam answer, which was deleted together with its author. Since there is no longer a user whose activity bumped the post, Community takes the blame.
The most frequent reason is 1), which was the cause of two of the three examples you linked. The rules for bumping are as follows:
the posts eligible for bumping are those scoring >= 0 that have gone at least 30 days with no activity, have at least one non-deleted answer scoring 0 and none scoring more than that, and no accepted answer (also, they can't be locked or closed).
So, if a month ago the site had either more answers or fewer votes than usual, that would create a backlog of questions with 0-score answers for Community to bump.
The bumping activity is more in-your-face nowadays, due to recently introduced post notices: How can we make the purpose of Community “bumping” more obvious?. This may increase the perceived impact of Community on the front page of the site.