Heya @SUM1, I really appreciate you taking the time to report the issues like you have been doing over the last few months on Page Previews. The HTML-based extracts are now in production. I took a look at your reports and examples and things seem to be improved. To summarize here's what I'm seeing now.
- IPA is not properly removed - no extra spaces!
- Post-nominal letters are not properly removed in link previews - In the George Harrison example it's fixed, but not the David Gilmour. The only difference is that one article contains the comma in wikitext, the other does not. I think, like hatnotes that are not a template, this is something Page Previews is going to goof on due to the inconsistency on how post-nominals are added to articles.
- Formulas are not properly displayed in link previews - Formulas are looking great! Let me know if you see any weirdness in your experiences.
- Link previews are occasionally only one sentence long - Your example and a smattering of other stubs I took a look at are more useful (and nicer looking IMHO) than before.
- Hatnotes which are not organized as templates are shown by mistake in link previews - As others pointed out in the discussion, Page Previews isn't smart enough to suss out when something should be a template and it's not. I don't know if much on the feature's end can be done, but I'm happy you reported it and that other editors chimed in with some suggestions.
- Only one line of text is shown in link previews sometimes - Again, it seems the switch to HTML excerpts has remedied this issue.
- Link previews are occasionally blank for pages with content - We had some similar issues reported in Phabircator and this looks to have been resolved!
I wanted to follow up with you and more importantly to say thanks for your help and patience. The team is working through some known issues and I'm happy to hear from you if you find more in your adventures.