This seems to be a font issue. Your screen shows WYSIWYG, while in the tag-only view such characters should already be visible in Studio. Looks like someone during the translation has copied some characters which are not included in the font.

It could be a font issue, but I can't get the tags. I searched how to include the formatting tags and it works when I make something bold. But the so-called spaces haven't changed:

Also, there was no hit from the TM, so it can't have come from there.

Oh, sorry. I must have missed something in your comment.

Well, what can have caused these signs are keyboard shortcuts inserting some characters outside from the visible charmap. These can come from the auto suggest function or from the MT. You see them as spaces in Studio, but these are not recognizable for Word and thus replaced by some strange symbols. In fact I cannot tell you where these exactly do come from, but the simplest solution is to delete these and forget about it. Only if that will be repeating itself more often there will be a need to investigate further.

Have you done any copy & paste here from Internet or other app?

Oh, sorry. I must have missed something in your comment.

Well, what can have caused these signs are keyboard shortcuts inserting some characters outside from the visible charmap. These can come from the auto suggest function or from the MT. You see them as spaces in Studio, but these are not recognizable for Word and thus replaced by some strange symbols. In fact I cannot tell you where these exactly do come from, but the simplest solution is to delete these and forget about it. Only if that will be repeating itself more often there will be a need to investigate further.

Have you done any copy & paste here from Internet or other app?