I've gone through articles that had 'nowiki' and VisualEditor tags in hewiki to try and find the common error, and as far as I can see, 90% of the errors involve quotes (") and the others are * and |

Examples:

https://he.wikipedia.org/w/index.php?title=%D7%A2%D7%95%D7%A4%D7%A8_%D7%A2%D7%99%D7%A0%D7%99&curid=309950&diff=15774877&oldid=15774872

https://he.wikipedia.org/w/index.php?title=%D7%94%D7%90%D7%A8%D7%99_%D7%A4%D7%95%D7%98%D7%A8_%D7%95%D7%90%D7%95%D7%A6%D7%A8%D7%95%D7%AA_%D7%94%D7%9E%D7%95%D7%95%D7%AA_(%D7%A1%D7%A8%D7%98)&curid=794595&diff=15773383&oldid=15733742

https://he.wikipedia.org/w/index.php?title=%D7%9E%D7%95%D7%A2%D7%A6%D7%AA_%D7%94%D7%AA%D7%9C%D7%9E%D7%99%D7%93%D7%99%D7%9D_%D7%95%D7%94%D7%A0%D7%95%D7%A2%D7%A8_%D7%94%D7%90%D7%A8%D7%A6%D7%99%D7%AA&curid=73014&diff=15770323&oldid=15756104

https://he.wikipedia.org/w/index.php?title=%D7%90%D7%9C%D7%99_%D7%A4%D7%99%D7%A0%D7%99%D7%A9&curid=144088&diff=15769264&oldid=15724086

https://he.wikipedia.org/w/index.php?title=%D7%93%D7%95%D7%A7%D7%98%D7%95%D7%A8_%D7%94%D7%95_-_%D7%9E%D7%A4%D7%9C%D7%A6%D7%95%D7%AA&curid=1085331&diff=15768361&oldid=15766030

https://he.wikipedia.org/w/index.php?title=%D7%A1%D7%A8%D7%98_%D7%90%D7%A8%D7%91%D7%A2-%D7%9E%D7%9E%D7%93&curid=1156586&diff=15764947&oldid=15051822

https://he.wikipedia.org/w/index.php?title=%D7%9E%D7%A0%D7%97%D7%9D_%D7%A4%D7%A8%D7%95%D7%A9&curid=33000&diff=15764545&oldid=15571348

https://he.wikipedia.org/w/index.php?title=%D7%A2%D7%95%D7%9E%D7%A8_%D7%93%D7%9E%D7%90%D7%A8%D7%99&curid=908862&diff=15763688&oldid=15763681

https://he.wikipedia.org/w/index.php?title=%D7%A2%D7%93_%D7%A2%D7%A6%D7%9D_%D7%94%D7%99%D7%95%D7%9D_%D7%94%D7%96%D7%94_(%D7%A1%D7%93%D7%A8%D7%AA_%D7%98%D7%9C%D7%95%D7%95%D7%99%D7%96%D7%99%D7%94)&curid=1016962&diff=15762484&oldid=15762481

https://he.wikipedia.org/w/index.php?title=%D7%9E%D7%91%D7%A6%D7%A2_%D7%A6%D7%95%D7%A7_%D7%90%D7%99%D7%AA%D7%9F&curid=1201545&diff=15761499&oldid=15761352

This might be an issue of bad character escaping or encoding.

This seems to also happen in the English wikipedia with quotes and asterix characters.

Examples:

https://en.wikipedia.org/w/index.php?title=Scar_(The_Lion_King)&curid=30258014&diff=619292425&oldid=619246147

https://en.wikipedia.org/w/index.php?title=Scar_(The_Lion_King)&curid=30258014&diff=619165895&oldid=619158383

https://en.wikipedia.org/w/index.php?title=Ravi_Babu&curid=24981592&diff=618944152&oldid=611211776

https://en.wikipedia.org/w/index.php?title=Adoni&curid=2329629&diff=618931054&oldid=618930241

https://en.wikipedia.org/w/index.php?title=Mia_Freedman&curid=10942134&diff=618755773&oldid=618669491

(Several <nowiki> tags right after quotes)
https://en.wikipedia.org/w/index.php?title=Rathmore,_County_Kildare&curid=43246971&diff=618885701&oldid=618885287

(Around an asterix)
https://en.wikipedia.org/w/index.php?title=Tulluru&curid=6910687&diff=618802171&oldid=618802085

After further analysis, here are the results:

Most of the nowiki problems seem to happen due to typing wikitext in the editor. For instance, typing ''word'' or '''word''' instead of marking the word as italics or bold, or typing literal == which VE then marks as =<nowiki/>= to prevent wikitext'ifying the result.

There are, however, some typing issues we could work on to make the experience easier on users:

1. Users typing a space at the beginning of a paragraph; this seems to be a mistake most of the time. Since a space at the beginning of a paragraph in wikitext transforms the paragraph to a <pre>, VE adds a <nowiki /> tag after it. It might be better if we strip those spaces when we save the page.

2. Users sometimes add list items by typing the literal * at the beginning of a line. While this is wikitext function (so VE wraps it with <nowiki>) it actually might make sense to try and transform any * at the beginning of lines to new bullet points; this is a the behavior that LibreOffice and Word are following, so it might be reasonable to have VE follow suit.

There are very few <nowiki> tags that I saw that are actual corruption. A new one that was reported recently on hewiki might show a problem with reading the wikitext headings wrong, so upon deleting the heading all that's left are == which VE marks with =<nowiki>= (see here: https://he.wikipedia.org/w/index.php?title=%D7%A9%D7%95%D7%9C%D7%97%D7%9F&diff=15566083&oldid=154101 )

Some, like this one, seem to show a problem with existing <nowiki> tags that then get "worse" after edit: https://en.wikipedia.org/w/index.php?title=Rathmore,_County_Kildare&curid=43246971&diff=618885701&oldid=618885287

We might want to consider marking any existing <nowiki>, perhaps?

In any case, these seem to be fairly uncommon and we should treat them on a case to case basis.

Corruption bugs are handled independently on a case-by-case basis; nothing in this list indicates that the <nowiki> issue is specifically related to Hebrew or RTL.

Space in the beginning of paragraphs is followed up in this bug: https://bugzilla.wikimedia.org/show_bug.cgi?id=66628

Transforming a star into bullet point (in the beginning of a line) is followed in this bug report: https://bugzilla.wikimedia.org/show_bug.cgi?id=51408

The rest seem to be errors in typing wikitext.