Since 0.5.3 is currently unusable, I'll have to report the bug I have found for the last working version which is 0.5.1. I have noticed that every message sent through roundcube has a leading space character in every line except the signature delimiter "-- ". The signature itself also has a leading space in each line. This looks bad and roundcube should not reformat my messages in this way.
please search the forum before posting, you'll see that the problem with spaces at the start of lines has already been reported and fixed.