The subject is a bit cryptic because I don't know whow to briefly describe the subject :-\
It's somehow related to https://community.sdl.com/product-groups/translationproductivity/f/90/t/13319 thread...

There seems to exist some linguistic rule in certain languages or certain contexts in these languages (Spanish and Brazilian Portuguese at least) that if certain parts of the source English text is left untranslated (e.g. UI terms, etc.), this untranslated text should be formatted in italic.
This means adding formatting which is not present in source...

It was mentioned several times in the forum that "CAT tools are not intended for formatting text"... and it was also mentioned several times that "...though, in certain formats like Office it is possible to add/change formatting"... I know all that.

Now, I need to know whether the following is somehow widely known and even intended and designed behavior, or whether it's rather some "side effect" and/or "positively-affecting bug" or so...

• There is an InDesign source document...
• ...i.e. an IDML file is localized and imported back to InDesign
• PDF is exported from InDesign and sent to client's client for review
• commented PDF comes back from this review, with comments like this:
  
• now Bilingual Word for External Review is exported from Studio and sent to reviewer to implement the comments
• reviewer implements the requirement for adding italic by manually adding <italic> tags in the Word file - and this is something what I'm completely perplexed by and need to know what the heck is going on here and if it's 'allowed' and supported action
  
• the bilingual Word file is imported in Studio (which really imports the added italic formatting - it's then visible in the target segment in Studio :-O)
• ...and even more suprisingly, this italic formatting is then correctly populated even into the IDML file and further in the InDesign, where - if the font used for that particular text contains italic style - the text (the word "grayscale" in this example) is then correctly formatted in italic :-O

To be honest, this all seems too crazy to be intended behavior...
But I was informed by DTP engineers that they use this practice for long time on many projects... :-O

So, can I have some official statement to this?

Background information - we have problems with this process when the used font doesn't actually contain italic style, but a separate differently named font needs to be used for italic; in such case the text does NOT appear in italic automatically, but DTP engineer must add the extra font in the InDesign project (it's not there because the original source does not use italic)... and if DTP engineer forgets to add the extra font, the italic formatting is missing and client is complaining...
So I'm trying to find out if the entire practice with adding extra <italic> tag is not just completely wrong by nature.