I have never thought I have heard the pattern "especially so [you]…" and when I came across yesterday it did not sound right. Of course if not a typo then it must be correct being in Merriam Webster's so does it sound "good English"-whatever that means?
Some Patterns familiar are:
- especially when/where/… you
- especially to do/make/…
- especially doing/making …
slice and dice chiefly US : to divide something into many small parts
especially so you can use the result for your own purposes
▪You can slice and dice the data any way you want.
Source: Merriam-Webster's Advanced Learner's Dictionary
Best Answer
Does it make more sense if we insert that?
If not, then let us consider one of the definitions of so.
So we can reword the original into
Apparently you (OP) think that a comma would make sense "when spoken", but I personally didn't think it made a difference. This is because, typically, in the usual dictionary writing style, the word especially refers to the text the proceeds it, not precedes it.
I think there are a number of things that are strange with this entry. Two that I can formulate are 1. The entry goes from writing in the infinitive style (I don't know the correct name) to dropping the infinitive style and addressing the reader. 2. The entry drops the "that" in "so that".
Dictionary entries not usually address the reader. So that was odd. I also think "so that" sounds better, per se. Not because it is any more correct, but simply out of habit.
Maybe the learner dictionaries are different, or this particular entry is an odd, but I might have written it as