Thread:VisualEditor/Feedback/Level 2 header on a column cell on a table on VisualEditor?/reply

Since you can add headers of any level in a table, this is more a failing of wikitext than the editor.

While yes, it's poor form to add headers in tables, it also has a few limited use cases (table of contents anchors in a long table, for one). It may not be the case on any of the MediaWiki projects, but I know of personal sites that do put headers in tables.

If you were talking about the header appearing in a seemingly offset second line of the cell (as per your image), that's likely due to an obligatory line break required in order to create the header, since you can't create a header on a line that starts with a pipe character.