I actually think this is intentional, and it’s what @MarcLarcher had asked for, isn’t it?
In French, according to typographic rules, double punctuation marks such as : ; ! must be preceded by a narrow non-breaking space, and very few fonts provide one. Academico does!
Yes, I think Daniel did answer to my request at some point, which was a relief, because before that, I had to re-tweak the font each time there was an update to it (and there have been lots of them!). Sorry for not remembering how this all ended 
I am using Nepomuk
I cannot duplicate your result using Nepomuk. Paragraphs with and without narrow no-break spaces have the same line spacing for me.
After a computer re-start, I do not have the problem, so no issue.
Thank you for checking.