You don't need to keep special characters when converting text to Vietnamese URLs. For example, the title:

"Ghi hình ban đêm có màu, rõ nét hơn cả mong đợi!"

can be converted to:

"ghi-hinh-ban-dem-co-mau-ro-net-hon-ca-mong-doi"

Notice that I removed the comma “,” and the exclamation mark “!”.

You can refer to this tool for assistance: lucidgen.com/cong-cu-xoa-dau-tieng-viet/