IDLE: make smart indent after comment line consistent

GitHub fields:

assignee = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2018-02-23.03:41:55.602>
labels = ['3.8', 'expert-IDLE', 'type-bug', '3.7']
title = 'IDLE: make smart indent after comment line consistent'
updated_at = <Date 2018-02-23.03:54:11.575>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2018-02-23.03:54:11.575>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2018-02-23.03:41:55.602>
creator = 'terry.reedy'
dependencies = []
files = []
hgrepos = []
issue_num = 32918
keywords = ['patch']
message_count = 2.0
messages = ['312613', '312614']
nosy_count = 2.0
nosy_names = ['terry.reedy', 'cheryl.sabella']
pr_nums = ['5755']
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32918'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']