Originally Posted by Ripplinger
You would think that software across all platforms could follow certain rules to avoid orphans of certain characters.
There problem here is that different languages have different rules.
What you've done, using the Word Joiner character, is entirely correct. That Sigil and calibre don't display it correctly is a bug in their display.
Unfortunately, you can't tell what software people are going to use to read your book.
If it displays OK in Adobe Digital Editions, it will display OK in most ebook readers that read ePubs.
Whether the converted Kindle book will display nicely on Kindles is unknown to me.