I wonder whether this is still happening. I don't remember seeing it recently.

Still happening, in different languages. For example at https://diq.wikipedia.org/wiki/Karber:Runab_WMF/diq-test-page

Here too

https://en.wikipedia.org/w/index.php?title=%C3%89lage_Diouf&type=revision&diff=679497648&oldid=679484697

@ssastry, could this be a Parsoid issue?

In T98018#1611389, @Magioladitis wrote:

Here too

https://en.wikipedia.org/w/index.php?title=%C3%89lage_Diouf&type=revision&diff=679497648&oldid=679484697

This is a curious example. Here's a spinoff: T112739.

@Amire80: I don't know what I am looking at. In the enwiki example above, I don't see Modèle ? Maybe show up on IRC sometime and we can chat more and we can then update this ticket accordingly.

@ssastry, in the enwiki example, it's "Template:", not "Modèle:" (which is for frwiki, French translation of template).
The diff is the correction made on the original edit, so "Template:" appears on the left side.

I am confused still. In the left hand column (on an enwiki page), it uses Template: prefix which is the right prefix on enwiki right?

In any case, I don't think whatever the issue is is related to Parsoid. Parsoid uses data-mw.parts[].template.target.wt to generate the transclusion. So, it just emits whatever it finds there. But, if some special Parsoid support is required here, that is something that I need to understand better.

I don't know if this problem has anything to do with Parsoid : the problem is that sometimes, CX creates articles where template calls are prefixed by an unnecessary "Template:" for enwiki, "Modèle:" for frwiki, ... (the localized name of the Template namespace on the wiki). The prefix shouldn't be added, it's totally unnecessary and creates unnecessary complex syntax.

That's just one of the many problems with CX....

In T98018#1647086, @ssastry wrote:

I am confused still. In the left hand column (on an enwiki page), it uses Template: prefix which is the right prefix on enwiki right?

There should be no prefix. It should not have Template: or Modèle:. {{Template:cite web|....}}} should just be {{cite web|....}}

In T98018#1647117, @Bgwhite wrote:

In T98018#1647086, @ssastry wrote:

I am confused still. In the left hand column (on an enwiki page), it uses Template: prefix which is the right prefix on enwiki right?

There should be no prefix. It should not have Template: or Modèle:. {{Template:cite web|....}}} should just be {{cite web|....}}

Ah, ok. I, for some strange reason, totally misread the description and comments (blame it as late evening tiredness :) ) ... I thought that the wrong-language prefix was being added. But, the issue is more that the prefix shouldn't be there at all.

This is still happening. See https://en.wikipedia.org/w/index.php?title=C%C3%BAllar_Vega&type=revision&diff=684709457&oldid=662429942

As part of of fixing T136817: MT: A 'Restore' after 'Clear paragraph ' miss data-mw and data-parsoid attributes, this issue was identified and fixed with https://gerrit.wikimedia.org/r/#/c/292528/ and https://gerrit.wikimedia.org/r/292548

From the commit message:

As per https://www.mediawiki.org/wiki/Specs/HTML/1.2.1#Transclusion_content
data-mw.parts.template.target.wt can have the template name like "foo"
or "Template:Foo". Their resulting wikitext will be slightly different
as in: {{Foo}} or {{Template:Foo}}, but the resulting HTML rendering
for both of this is same - Template Foo will be used. You can try this
by this example {{Template:En}} and {{En}}

Content translation was adapating the templates with wt set as Template:Foo
so far. It works as per the above explanation. But when you try to restore
such translation drafts, Template names were read as Template:Foo and processing
blindly adds another Template: prefix resulting deconstruction of such
templates by not finding it in target wiki.