Don't skip over tabs/spaces, when they are the only things on that line.
This shows why I think it should be like this. Have your cursor under "Fifth line." and run `xah-beginning-of-line-or-block'. The cursor will now move under "First line.", skipping all the lines in between.
First line.
Second line.
Third line.
Forth line.
Fifth line.
Don't skip over tabs/spaces, when they are the only things on that line.
This shows why I think it should be like this. Have your cursor under "Fifth line." and run `xah-beginning-of-line-or-block'. The cursor will now move under "First line.", skipping all the lines in between.