Open the "First Look" demo app for rich text editor. Delete all the text. Insert a table with 5 columns and 2 rows. Select first 2 columns (4 cells in total). Merge these cells. The merged cell should have the width of 2 normal columns. Save this document as RTF. Open the document. The width of all columns is wrong. The merged cell now is wide as one normal column.

It seems that two issues are combined into one problem. First, two merged columns are converted into one column. If I try to split the merged cell before the save I get my two columns back, but after the save there are only two rows after the split, but only one column. Second, the "AutoFit to Window" option is messing with the column widths. If I set the table to "Fixed Column Width" then the table remains unchanged after reload. But this option doesn't work if the merged cell is selected. Must unselect it first, or change the option before the merge. But this minor annoyance is not the part of this bug report.