displaying mean with sem or confidence interval When I look at scientific papers, bar charts I usually come to see are shown with mean +/- sem.

As stated here,


  When standard error (SE) bars do not overlap, you cannot be sure that
  the difference between two means is statistically significant


and 


  If 95% CI error bars do not overlap, you can be sure the difference is
  statistically significant (P &lt; 0.05).


Even if the reverse is not true, why don't we always use the confidence interval instead of the sem in bar charts, since it seems more informative ?
My guess: SEM needs to be multiplied with the constant from the probability distribution of concern (e.g. t-distribution) to become confidence interval. In some study, sample size is so low that the constant can make the bars look huge.

Yet, in your cited link there is another important phrase:


  No surprises here. When SE bars overlap, (as in experiment 2) you can
  be sure the difference between the two means is not statistically
  significant (P>0.05).


So, SE may not serve to tell if there is a significance difference, but can tell if there is likely none. Depending on the researchers' motive this could be a good feature.

What I'd advocate, however, is not to believe these visual comparison as if they are definitive. One illustrative explanation can be found in this online pdf.

Anyhow, a graph is a graph and as long as it's labeled clearly I'd consider that acceptable. What can confuse people is when the authors use this kind of error-bar like device but did not footnote what the bars represent.