How to link to SObject within Case Feed in console-friendly fashion?

I have a requirement to add a link from one case to another within the case feed. This will happen from a future method called from trigger context, so it should be bulk safe. For this reason, I'd like to insert FeedItem records directly instead of using ConnectAPI.

I've tried a few things with partial success:

• I tried to insert a FeedItem of type TextPost with IsRichText set to true, with an embedded <a> tag pointing to the url '/'+ caseId. This gave an error that the link must begin with 'http:', 'https:', etc.
• I changed the link to 'sfdc:'+ caseId (the form required for img src attributes when using RichText), but got the same error.
• I changed the link to a full SFDC url (URL.getSalesforceBaseUrl().toExternalForm() +'/'+ caseId), which generated the error, "Context user does not have permission to create rich text in feed." I can find no documentation of this error, but I have seen claims that you can only insert a RichText TextItem via SOAP API.
• I switched to creating a FeedItem of type LinkPost. Again, I had to use a full URL. This works, but the link opens in a new browser tab instead of within a new Console tab.

This last will work if no other choice, but I'd really prefer a way to show a link to the other case that would open the other case directly in the current Console. I don't particularly care what FeedItem type I use. Is this possible?