Hi Zlatka Zaharieva 

I have also run across many of these tags in IDML files (i.e. the tags with "nfa=true")

When I translate I always follow the corresponding PDF, so I generally ignore these tags or combine them unless there are formatting changes like bold or italic or a different font.

If they appear to be there just to make the lines justify or break nicely, then they are not needed. The spacing needed to justify or break the lines in the translation will be completely different anyway.

So in the example you provided, since the tags all include the same font name and size, when translating I would probably just use one tag pair to format all of the text in each segment (unless there was a section of bold or italic text in the PDF), instead of trying to figure out where to place each and every one of the tags.

I might be wrong in my interpretation of these tags as being mainly for spacing, but no clients have complained yet :-)

Best regards,
Bruce Campbell
ASAP Language Services

That thread is somewhat old, but the issue is still relevant today, and not only for IDML files. Actually, it is not really an issue, since it does not prevent to translate or re-export the document. It just make the translation more complex, since it is visually a mess. 

IMHO, the issue comes from the initial document. For instance, when the author, writes a sentence in the default color, which is usually black, and nevertheless specify black for some words in it, you will get useless black formatting tags in your sdlxliff, because those formatting tags are already in the source document. It is the same if you put some word in bold, then decide later to put also in bold the next following word, you will get two pairs of bold tags instead of one. and so on. That happens often when a documents had several revisions. 

As Bruce suggested, you can consolidate the pairs of tags. For instance, if you have multiple Arial 10 pairs, you can remove them and only put an opening Arial 10 tag at the beginning of the sentence and a closing tag at the end.

Also, there are features really handy to improve the visibility of a segment with many tags in the ribbon:

You can see below a view where I streamlined the formatting tags:

Now, a view of the same where formatting tags are hidden (but still there — actually, the text is wysiwyg):

And now a view with just tags IDs, which allows to focus on the translation as such and easily check you did not omit or add important tags:

Of course, you can use several combinations of those views. It really facilitates and accelerates the process with tagfull segments.

HTH