Span style is not working in QTextEdit

[Brandybuck]

Qt's rich text rendering engine is not a W3C compliant HTML renderer. I know that's sad to hear, but it's true. You will be very frustrated if you pretend that it is. For example, it doesn't support the "float" style properties (nor most other CSS properties). See "Supported HTML Subset" in Assistant.

You can do what you want in a <table>, however. Make a two cell table, and align one cell to the left and the other to the right.