Dashes issue re-emerges

So I’m typing along, and for some reason I need a series of dashes in the text.

so…

I type a series of hyphens, expecting to see every two hyphens convert to an Em-dash.

Nope.

First two stay there (expected), type the third, the first two form an Em-dash, the third is beside it (still expected). Type the fourth, I have just one em-dash, no hyphens, and the line height changes slightly (it’s adding about 6 points of space above the line, I think). NOT expected. and no invisibles (I looked).

Font is Dejavu Serif, Book, 14 point. Spacing 1.1x. This template is NOT converted from 1.9.x; it’s created new with 2.9.0.8 (I think).

I have been able to replicate this. In a new paragraph, I typed in text with some word combinations separated by two hyphens–wihch yielded an em-dash; three hyphens–which yielded an em-dash with the third hyphen disappearing; and four hyphens–yielding an em-dash, and a box figure right/down (U+250C on Character Map) with line spacing for all the text changed from “Single” to “Multiple at 1.09”, not just for the text paragraph, but for all others as well.

2.9.0.11

Bug is still present.

two hyphens = one emdash
four hyphens = one emdash

Tried it in Beta 11 as well, with same results.