Our software uses a TTMSFNCRichEditor component to insert text.
Users have reported a strange behavior if you paste a text in place of a text that includes the 'end of line'.
The same problem can be verified in the VCL demo 'RichEditor' included in the installation of the package 'TMSFNCUIPack'.
Do you have a more precise description, as with just this description I cannot see a problem.
I select a line in the memo and select the line feed along and then paste text from the clipboard and I cannot see a problem.
I made a video (https://ccar05.lsis2.it/TMS_RichEditor_Demo.webm) where I replicate the anomaly in the RichEditor demo:
the first paste (CTRL+V of the word 'Demo'), on a highlighted word in the center of the line, works as expected;
the second paste (CTRL+V of the word 'Demo'), on highlighted words including the 'end of line' shows the anomalous behavior.