It looks to me like MediaWiki template parameters are case sensitive. So the behaviour of VE/TD seems correct.

AlexMonk-WMF, Can you confirm if i understand correctly. TemplateData aliases should work so that if there is in TemplateData parameter {{{Title}}} with alias {{{title}}} and it is used in article like this:

{{foo|title=Sometitle}}

Then in visual editor when user is editing the template then there is in edit form row for "Title" with empty value and row for "title" with value "Sometitle". In VE user interface both are identical and there is no way to tell why there is two different titles and where values are coming..

This is how aliases is supposed to work? If so then this behaviour should be documented to somewhere like to https://www.mediawiki.org/wiki/Help:TemplateData#Parameter_aliases

I don't think TD's aliases are used for anything except parameter searching in VE? In any case if we're mishandling aliases you need to open a new task for that.

Actually, that and this sound kind of related to T143650 which I have yet to figure out