this was a damned elusive one to find... but...
Go to edit templates... edit: newpost_disablesmiliesoption
In that code add
checked="checked" to the input field and it will be auto checked everywhere it appears. Remove the code: $checked[disablesmilies]
It seems like there may have been an option for this somewhere in vbulletin options but I have no idea where... this will override that.(if it exists)
Example. change:
Code:
<input type="checkbox" name="disablesmilies" value="1" id="cb_disablesmilies" tabindex="1" $checked[disablesmilies] />
to
Code:
<input type="checkbox" name="disablesmilies" value="1" id="cb_disablesmilies" tabindex="1" checked="checked" />