Sharepoint Online : Append text changes not getting reflected in column

[vkartik]

Hi,

I am enabling "Append changes to exiting text" in 2 columns but it is only getting reflected in one but not in another . I have compared all the settings and both columns are exactly same. Both columns are "Multiple line of Text" columns , "Not Required" ,"Unlimited length" is set to false ,enabled "Append Text to existing Text" for both.

Not sure why this is happening . Following is the screenshot

"Append changes to existing Text" is working for Doc Comments column but not for Post Approval Comments column.

Kindly let me know cause and possible fix for this issue
Thanks

[#2]

Only difference I noticed is, "Plain Text" is allowed in Doc Comments columns and for Post Approval Comments "Enhanced Rich Text" was allowed , can this be the cause.
Also I changed "Enhanced Rich Text" in Post Approval Comments column to "Plain Text" , still "Append Text" changes are not getting reflected