Thanks for your report. Unfortunately I have trouble understanding it, since there are different possible interpretations to “select comment” in Okular.

I understand that you created an underline annotation (say, a black underline). After that:
a) Did you deselect the underline annotation tool and double-clicked the annotation in the document view area, so a black annotation comment window opened?
b) Or did you select the popup comment annotation tool and clicked on the underline annotation to add a comment to it?

In case of a, I don’t know what you mean with the right side and the left side, and the position relationship. Can you add a screenshot of the problem, or even a screencast?

In case of b, you possibly misunderstood the annotation workflow of Okular. To add a comment to an existing annotation, you need to deselect the annotation tool (e. g. by clicking the “Browse” tool), and then double-click the annotation in the view area, or right-click it and select “Open popup note”. However, the comment will not be visible unless you explicitely double-click the annotation again. If the comment should be obviously visible, you need to create a second annotation of type “Popup note” or “Inline note”.

(In reply to David Hurka from comment #1)
> Thanks for your report. Unfortunately I have trouble understanding it, since
> there are different possible interpretations to “select comment” in Okular.
> 
> I understand that you created an underline annotation (say, a black
> underline). After that:
> a) Did you deselect the underline annotation tool and double-clicked the
> annotation in the document view area, so a black annotation comment window
> opened?
> b) Or did you select the popup comment annotation tool and clicked on the
> underline annotation to add a comment to it?
> 
> In case of a, I don’t know what you mean with the right side and the left
> side, and the position relationship. Can you add a screenshot of the
> problem, or even a screencast?
> 
> In case of b, you possibly misunderstood the annotation workflow of Okular.
> To add a comment to an existing annotation, you need to deselect the
> annotation tool (e. g. by clicking the “Browse” tool), and then double-click
> the annotation in the view area, or right-click it and select “Open popup
> note”. However, the comment will not be visible unless you explicitely
> double-click the annotation again. If the comment should be obviously
> visible, you need to create a second annotation of type “Popup note” or
> “Inline note”.

Through your reminding, I seem to understand where I was wrong. Therefore, the problem should not be okular's bug, but my misoperation.

By select comment, I mean underline comments. By clicking on the left and right, I mean the left and right ends of the underline.

My improper operation is that when I use the underline comment to select a sentence, I do not invert the underline comment, but double-click to open a pop-up window to add comments. The error occurs when you double-click. Due to the mouse movement, I mistakenly selected a character. That is to say, in a sentence, I not only selected the whole sentence, but also selected a certain character. When I double-click to pop up the underline comment window, I may hit the underline of that character or the whole sentence. That's what caused me the illusion that clicking on the left and right sides of the underline would bring up different comments. In fact, I added two underscores without knowing it.

I'm sorry that my Chinglish is not accurate enough, and thank you for your patience.

Fine, then I just close this. :)

> My improper operation is that when I use the underline comment to select a
> sentence, I do not invert the underline comment, but double-click to open
> a pop-up window to add comments.
Yes, that is something that happens to me too. It’s a question whether I want “Continuous” mode enabled or not...