In typesetting, punctuation needs to avoid appearing at the start or end of a line. This means certain punctuation marks should not be placed at the beginning or end of a line.

For example, a left quotation mark should not appear at the end of a line, and a period should not appear at the beginning.

There are many ways to handle punctuation at line boundaries, such as borrowing a character from the previous line, hanging punctuation, compressing spacing, and so on. When I was a child writing essays on grid paper, if a punctuation mark was about to land at the start of the next line, I would always squeeze it into the last cell alongside the final character.

Example

Original text:

在学术工作中，我们可以会遇到一些外语论文
。英语可能还好，但读起来不如中文母语效率
高。

Hanging punctuation:

在学术工作中，我们可以会遇到一些外语论文。
英语可能还好，但读起来不如中文母语效率高。

Borrowing a character from the previous line:

在学术工作中，我们可以会遇到一些外语论
文。英语可能还好，但读起来不如中文母语
效率高。

Word processors like Word, image editing software like Photoshop, and browsers all support this kind of handling. Graphics libraries like JavaFX support it as well.

The manga translation software ImageTrans uses JavaFX for text layout, but the vertical text engine is implemented by myself. Currently, it has preliminary support for preventing periods from appearing at the start of a line.

References

https://www.thetype.com/2018/05/14501/