Why don't we display a red border conditionally ?

[mfranzke]

With #5526 we've fixed the bug #5525 that reported that our form fields weren't colored as valid if a successful message is missing.

The underlaying implementation results (initially) out of the following two issues:

• form elements: questioning mandatory validMessage for valid ones #2507
• Option to disable validation message #3096

We're wondering why these conditions have been introduced for the valid state initially, but not the invalid which would be much more relevant, depending on WCAG criteria (3.3.1)