bingle-admin wrote:

Prioritization and scheduling of this bug is tracked on Trello card https://trello.com/c/eALhrZdH

These empty cells aren't added by MobileFrontend, they appear in the desktop website, too (so, the source code output is the same for mobile, desktop and parsoid (they appear in parsoid, too)). The problem seems to be, that MobileFrontend has the following css rule.
.content table td, .content table th {
padding: 3px;
border: 1px #CCC solid;
}

which adds a border around all table cells. I don't know, why the border is added, but i think for better readability :/

Is it possiblle to remove the empty table cells from the template?

(In reply to Florian from comment #2)

Is it possiblle to remove the empty table cells from the template?

Last time I asked, it didn't seem possible.

Please add .content table.sinottico td to your MediaWiki:Mobile.css to remove this. We can't do anything our end, it serves the same HTML as desktop the skin is just styling it differently and you'll need to override it to meet your needs. Italian Wikipedia may also want to copy those styles relating to .sinottico [1] to Mobile.css

[1] https://it.wikipedia.org/wiki/MediaWiki:Common.css

I'm not sure all our table-based templates use that class. Should we override the mobile classes in all our templates?

What other tables have the same issue? If it's all tables you could of course create a generic rule for all tables and simply do
.content table td { border: none; }