The 'Locked' option is to make the select default, not for locking the comments for other users. I did change it to Green at my end, and the color for 'Replace text ' changed to Green.
Is it possible to share a screenshot of the Property box of 'Replace Text Tool'? To share the screenshot, refer to https://forums.adobe.com/docs/DOC-7043#jive_content_id_How_do_I_attach_a_screenshot
What is the dot version of Adobe Reader installed? To identify refer to Identify the product and its version for Acrobat and Reader DC
is it a Mac or Windows machine? Have you tried with other PDF?
We're here to help, just need more info.
Thanks,
Anand Sri.
The Locked box has nothing to do with making the selection the new default. It only serves to make it more difficult to change the properties of that specific comment. To do that you need to right-click the comment and select "Make Current Properties Default", or tick the box with that name under the comment's Properties.
I would recommend against using the "Replace Text" comment tool at all. It's a problematic one because it adds two kinds of comments at once (a Strikethrough and a Caret), which makes it more difficult to edit. Use a simple Strikethrough instead.