The {{Collapse bottom}} template generates the |}, and for it to work correctly as an end-of-table markup, it must be on a separate line. In the diff you linked, it was placed by Parsoid on the same line as the closing </syntaxhighlight> tag.

@matmarex Indeed that did the trick! But, ideally, there is a way to auto-detect/ fix this?

The Editing-team believes this ticket should be looked at by Parsoid, we are not prioritizing at this time.

In T227921#5334508, @matmarex wrote:

The {{Collapse bottom}} template generates the |}, and for it to work correctly as an end-of-table markup, it must be on a separate line. In the diff you linked, it was placed by Parsoid on the same line as the closing </syntaxhighlight> tag.

Parsoid doesn't know it needs to be a on a separate line ... does templatedata format specify this?

In T227921#5337750, @ssastry wrote:

Parsoid doesn't know it needs to be a on a separate line ... does templatedata format specify this?

Doesn't seem like it.

"notemplatedata":""

https://meta.wikimedia.org/w/api.php?action=templatedata&titles=Template:Collapse%20bottom&format=json&includeMissingTitles=1