The apostrophe is an escape character, needed to insert data with quotes into the MySQL database that contains MySQL control characters, such as the apostrophe.
I'm finding there are quite a few places in the Plogger code which do not strip out this extraneous slash, but you can fix it yourself pretty easily.
If you are comfortable editing PHP code, then you simply need to apply the stripslashes() function to any part of the display output that you want to remove the slash from.
If you aren't comfortable, then let us know where you want to have the slash removed from and we can give you the lines of code to change.