Sentence:  As far as possible this specification uses non-combining characters, however, in the cases tdot, TripleDot and DotDot Unicode only has <WSD>combining forms</WSD> of the accents, and so the entity replacement text starts with a space, to avoid the possibility that the expansion of the entity combines with preceding text. 
Meaning of the word marked with <WSD> tags:  A (character encoded) from a sequence of other characters instead of a (precomposed character).