is + depending on

[emsr2d2]

Yes, I saw that one already but it's a different case though. The depending phrase is required for sure for that one. However, in my case, I felt it is but it can stand alone without. That's the issue.

I would not write the original sentence without the comma.

Note my correction above. I don't know what the blue underlined part means.

[jutfrank]

You need a comma.

It doesn't matter how short the sentence is.

[PaulMatthews]

Hi,

The starting target score is 50-60% depending on the learner's skill level.

Is the above grammatically correct?

Thanks.

The starting target score is 50-60%, depending on the learner's skill level.
Yes, ideally you need the comma.

The preposition phrase is a supplement, a loosely attached element that is set off by intonation (and usually by punctuation) presenting supplementary non-integrated content.