Sure. It can be changed with CSS or directly through php file of the plugin if you wish. Can you please take a screenshot in order to verify that we talk about the same border line?
Thank you for responding so quickly. The screenshot is shown below.

Not all of the pages show the bottom line, which is difficult to understand. I assume the CCS would be placed in the “Additional CCS” under customize?
Dale
Exactly. You can use custom CSS code to override when needed.
What is the CSS code that removes the bottom border?
Dale
If this border is not visible at every page, it means that is doesnt come from my plugin.
Can you please share your URL?
Main site: http://physikon.net/
Page where [Read more] displays a bottom border (about 3/4 down page): http://physikon.net/?page_id=2082
Page where [Read more] does not display a bottom border: http://physikon.net/?page_id=2914
Another site where [Read more] always has a bottom order: http://the-physicist.com/?page_id=735
Dale
Seems that these borders are there because of my plugin and not a third party one, or a theme styling.
You can override their CSS valued and have them removed, by using this CSS code:
*[id^=’readlink’] {
border: none !important;
}
I placed this code into the additional CSS under customize, but it has no effect.
Dale
I can see it working fine on my inspector. I suggest you contacting theme developer in order to ensure that you paste your custom CSS code to the proper field, or use a custom CSS plugin if you are not familiar with such a task.
You can also edit index.php of my plugin and modify its code, but this is not advised.
I put it in the right place, and now it works great. Thank you.
Dale
One other question:
What is the CSS code to remove the double line at the base of the [Read more] button on mouse over?
Dale
Hi Dale.
Sorry for late replying.
You can use border:none option at every CSS element that you want to remove its border line.