Front / back focus: although the camera focuses and confirms that focus is obtained on a certain object the lens optically focuses either at a point closer to the camera (front) or at a point further behind (back) the actual focused object. Understanding Depth of Field - pay attention how aperture affects DOF, then read again the description of TS.
Lastly: there is a search function upper right hand and there is Google.
Yes, usually it's an issue about the lens. The camera measures and determines how much the focus ring of the lens has to move according the current blur image and the position of the focus element as reported by the lens. The respective focus command is given to the lens. If the lens is not at the correct focus position after executing the command then it's either an issue of focus motor not working properly or the position of the focus element does not match what the lens is reporting.
Some bodies have micro adjustment capabilities where the body can "learn" how much the lens is off (to back or front) and the focus command is adjusted accordingly. The other option is lens calibrating which is done at the respective service centers for the lens.
This is what catchlights mentioned: Depth of Field is too thin. Check the link that I posted earlier, use the calculator, enter your data (focal length, aperture, distance, 1.6x crop) and you can see how the results changes when you change from f/1.4 to f/22.
Hi, from all those lens test reviews I've read, there is no problem.
Most lens are 'soft' (blur) when you use their max aperture. Unless it's those super expensive one.
Therefore those cheap lens, even though they may have f2.8 constant for all focal length, using the max aperture will be blur. Maybe those lens review might be helpful before you commit to buying lens.
If you really do study the shots closely, you would indeed find the shot taken at f/1.4 to be soft.
Of course by taken a full frontal shot of the newspaper page, it's hard to tell. It may be good to take the page from an angle and tell yourself which character you are auto-focusing at, and examine that particular character closely to see if it is sharp at the character itself, or the character in front or behind it.
This problem plagued me for a while before Canon Service Centre checked and determined my 50mm f/1.4 to have a front focusing problem. Ever since the calibration, the focus point has no problem.
I would suggest you bring it back to CSC for a check esp if your lens is still under warranty. Otherwise you will never have peace of mind.