InDesign's default text shaping engine can't read font space kerning

I have all kinds of questions about this! but I really don't know where to start. I had an older version of your font installed when I started trying to replicate your issue, which led me to some surprising places as I poked around in your test file. I can manually kern words into place across spaces, and the font clearly has metrics meant to do so, but when Harfbuzz is on, the only way I can get the text to render as it does in your initial screenshot is to replace all of the spaces with non-joiners (U+200c) which is, of course, not a space character. 

So I wonder if this is an InDesign issue, or a Harfbuzz issue. Is it broadly speaking an issue with how the WRC handles spaces? Or is it something that can only be fixed upstream? I mean, reporting it to the InDesign dev team as a bug (by posting at indesign.uservoice.com) should be your first move in either case, I think. Once you've done so, post that link here, and request that your users vote on your posting at the Uservoice. Upvoting that post increases the likelihood that it will see attention from the InDesign developers. 

I made this simple little .gif to demonstrate what I think the issue might be, but showing it in Latin script, and comparing the behavior of the Adobe Paragraph Composer and the WRC. As you can see at the end of the loop, the only condition under which we can't manually kern a glyph past a space is in the WRC with Harfbuzz turned on. 

Hi @arifharoonkarim, 

Would you mind confirming if this issue persists in version 20.1? In the meantime, I'll check with the product team and share any updates with you.

Looking forward to hearing from you!

^
Abhishek