From top to bottom: Pasted table in VE -> Rendered page after save -> Source after save -> Table re-opened in VE
<thead> tags within a <table> are not parsed correctly. When saved they are saved as literals and not wikitext.
Version: unspecified
Severity: trivial
Attached:
<thead> isn't supported in wikitext
https://en.wikipedia.org/wiki/Help:HTML_in_wikitext#thead.2C_tfoot.2C_tbody
but should be stripped in this scenario (or the entire table switched to html syntax, but that's probably not what's intended).
Change 138731 had a related patch set uploaded by Arlolra:
Strip unsupported table tags when serializing
I think converting to html syntax might actually be what's intended. It's hard to say.
In the example I ran across, the header of the table I pasted did have <thead> in order to ensure that the header of the table was properly repeated across page breaks. It seems like it would be nice to preserve that semantic information.