I don't know why those characters are there. But you can easily get rid of it by copying from the result text box instead of from the conversion outputs
For example if you want the binary value, click the
BIN line to make the output changes to binary then copy
Of course this is just a workaround until there's a solid solution
In the current version (10.1907.24.0) if you right click directly on the number like the screenshot above then a context menu with "Select All" will be shown. To get Copy/Paste you must right click anywhere outside the number box
The issue has been reported in Calculator's repo: Copy paste result contains hidden character. Those characters have been specified as "by design"
Talked with @joshkoon offline and we think we can be smarter about when we include the extra hidden characters. Assigning to @joseartrivera to either fix this or, if we cannot remove the characters, close out bug as by design.
The issue has been fixed in this pull request. Checked with Calculator 10.2004.23.0 on my PC and no U+202C/202D characters anymore