After you set up a News Stream to show Content by filtering tags, you notice that Blog Posts and Documents that have the relevant tag in their comments, do not show up in the News Stream. However, the Questions and Discussions that have the relevant tags in their comments do show up in the News Stream.
This issue was identified as a bug and resolved in Jive Cloud release 3006.8 with the issue key JVCLD-143706 (release notes on Worx). While the Cloud upgrades are automatically deployed, if you haven't yet been upgraded or have chosen to stay on an earlier version and now would like to upgrade, please get in touch with your Account Manager/Executive to arrange for the upgrade.
After the upgrade, Blog Posts and Documents that have the relevant tags in their comments will show up in the News Streams as expected.