I'm using pgAdmin 1.16.0, against PostgreSQL 9.2.1 (but I see the same
thing against 9.1.6).
If I add a new table ("New table" from the object browser context menu
for "Tables"), while creating the table I can add column and enter
comments for those columns. Those comments get pushed to the
database, and the "SQL" tab of the dialog box shows the additional
statements which do this.
If I use the object browser context menu for an existing table and
choose "Properties...', I get a dialog that looks identical to dialog
for creating the table. It allows me to add a new column to the table
just like in the table creation case, and it ask for a comment on the
new column. But that comment gets thrown away. The SQL tab reflects
the alter table statement to add the column, but not the additional
statement to record the comment on that new column.
If I use the object browser context menu for the "Columns" property of
the existing table to add a new column, that method does record the
comment.
I found some emails in the archive from March 2008 that suggests this
was fixed by making the "comment" field read-only when changes to it
cannot be honored.
e.g. http://archives.postgresql.org/pgadmin-support/2008-03/msg00033.php
But it seems the fix came undone.
Cheers,
Jeff