It's a point on french grammar.
First some background. In some very specific usages, "ne" is not used for negation (as usual) but for marking a contrast (e.g. "Ca arrive moins souvent qu'on ne le pense"="it happens less often than people think").
As a french speaker I can tell you that it is purely grammatical: it is imposed on us by the form of the sentence. Omitting it is possible, but sounds informal.
Intuitively I would say that the specific usage of this "ne explétif" is when the contrast does not concern the two elements of the sentence directly. There is a mediation, for example through an intentional verb (there is a "that which" of some sort). In the example above: the comparison is not between what happens and the fact that people think, but between what happens and what people think.
I make this point because I disagree with the text you cite. To me this interpretation overthink a grammatical usage.
Now the text you cite asserts that:
- when a sentence does not use this "ne" (I would say in case of direct comparison), the speaker asserts something "impersonnaly". It's a simple, bare assertion the speaker endorses without any distance (this is how I interpret the unnecessarily complicated expression of "coincidence with the intention-to-signify": bare endorsement).
- sentences with this "ne" would be used to mark an affective distance between the speaker and something else. The speaker does not only endorse a position (some comparison), s/he also express how her own endorsement is involved by contrast to something. In the example above "it happens less often than people think", that would mean that the speaker emphasize the contrast between what s/he endorse (that it doesn't happen very often) and what other people think.
Again I would say that reference to the act of enunciation and to "personal" is unnecessarily complicated: what they really mean is "the speaker".
To me this is an artefact. Indirect comparisons (between something and "that which ...") often occur with an intentional verb (that which one think, belive, say). It seems then that it marks a contrast between what the speaker thinks and what others think/believe/say. The author conclude that "ne" is used to mark an affective distance between the speaker and "that which"... But I don't think it's true: it's only a grammatical mark of indirection.
For the affective aspect, well any utterance can be said to be affective and to involve implicit attitudes of the speaker, be it bare endorsement or not, and perhaps more so when intentional verbs are used and comparisons are made, but I wouldn't say that the "ne" is itself an affective mark.
It can be used without any intentional content: "il est plus grand qu'il ne l'était" (he is taller than he was). There is an indirection (it's a comparison between a size and the size that he had before) but I don't see any affective distance of the speaker in this sentence. It's a bare endorsement.
In other words, this is BS.