I have override system.xml file.
My label is overridden but comment field is not overridden. It's still take from core file. Any help should be appreciated. Thanks.
Core system.xml file code
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../Magento/Config/etc/system_file.xsd">
<system>
<tab id="lsc" translate="label" sortOrder="100">
<label>SLI Systems LSC</label>
</tab>
<section id="sli_feed_generation" translate="label" sortOrder="100" showInDefault="1" showInWebsite="1" showInStore="1">
<class>separator-top</class>
<label>Feed Generation</label>
<tab>lsc</tab>
<resource>Sli_Feed::config_feed</resource>
<group id="general" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<label>General</label>
<field id="enabled" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Enabled</label>
<source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
</field>
<field id="log_level" translate="label comment" type="select" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Log Level</label>
<comment>Please set to "Debug" if SLI support is required.</comment>
<source_model>SLI\Feed\Model\Config\Source\Log</source_model>
</field>
<field id="version" translate="label" type="label" sortOrder="3" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Version</label>
<frontend_model>SLI\Feed\Block\System\Config\Version</frontend_model>
</field>
</group>
<group id="feed" translate="label" type="text" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Feed Settings</label>
<field id="advanced_pricing" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Advanced Pricing</label>
<comment>Enable if need advanced prices from: Catalog Price Rules, Group or Tiered Pricing.</comment>
<source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
</field>
<field id="include_out_of_stock" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Include Out of Stock Items</label>
<source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
</field>
<field id="generate" translate="label comment" type="button" sortOrder="2" showInDefault="1" showInWebsite="0" showInStore="0">
<label>Generate Feed</label>
<frontend_model>SLI\Feed\Block\System\Config\Generate</frontend_model>
<comment>Manually generates feed. If FTP is enabled, also sends the feed.</comment>
</field>
</group>
<group id="ftp" translate="label" type="text" sortOrder="3" showInDefault="1" showInWebsite="1" showInStore="1">
<label>FTP Settings</label>
<field id="enabled" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Enabled</label>
<source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
</field>
<field id="user" translate="label comment" type="text" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
<label>FTP User</label>
<comment>Provided by SLI.</comment>
<depends>
<field id="enabled">1</field>
</depends>
</field>
<field id="password" translate="label comment" type="obscure" sortOrder="3" showInDefault="1" showInWebsite="1" showInStore="1">
<label>FTP Password</label>
<backend_model>Magento\Config\Model\Config\Backend\Encrypted</backend_model>
<comment>Provided by SLI.</comment>
<depends>
<field id="enabled">1</field>
</depends>
</field>
<field id="host" translate="label comment" type="text" sortOrder="4" showInDefault="1" showInWebsite="1" showInStore="1">
<label>FTP Host</label>
<comment>Provided by SLI.</comment>
<depends>
<field id="enabled">1</field>
</depends>
</field>
<field id="upload_path" translate="label comment" type="text" sortOrder="5" showInDefault="1" showInWebsite="1" showInStore="1">
<label>FTP Upload Path</label>
<comment>Provided by SLI.</comment>
<depends>
<field id="enabled">1</field>
</depends>
</field>
</group>
<group id="product" translate="label" type="select" sortOrder="4" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Product Attributes</label>
<field id="attributes_select" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Attributes to include</label>
<frontend_model>SLI\Feed\Block\System\Config\Form\Field\FeedAttributesConfig</frontend_model>
<backend_model>Magento\Config\Model\Config\Backend\Serialized\ArraySerialized</backend_model>
<comment>
<![CDATA[
The following attributes are automatically added to the feed: <br />
<ul style="margin-left: 2em;">
<li><small>attribute_set_id</small></li>
<li><small>categories</small></li>
<li><small>child_ids</small></li>
<li><small>created_at</small></li>
<li><small>entity_id</small></li>
<li><small>final_price</small></li>
<li><small>has_options</small></li>
<li><small>is_salable</small></li>
<li><small>is_virtual</small></li>
<li><small>max_price</small></li>
<li><small>min_price</small></li>
<li><small>minimal_price</small></li>
<li><small>name</small></li>
<li><small>price</small></li>
<li><small>special_from_date</small></li>
<li><small>special_price</small></li>
<li><small>special_to_date</small></li>
<li><small>request_path</small></li>
<li><small>required_options</small></li>
<li><small>sku</small></li>
<li><small>tax_class_id</small></li>
<li><small>tier_price</small></li>
<li><small>type_id</small></li>
<li><small>updated_at</small></li>
<li><small>url_key</small></li>
<li><small>visibility</small></li>
<li><small>image</small></li>
</ul>
]]>
</comment>
</field>
</group>
</section>
</system>
my custom system.xml code
<?xml version="1.0" encoding="UTF-8"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
<system>
<section id="sli_feed_generation" >
<group id="product">
<label>Product Attributes AData</label>
<field id="attributes_select" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
<comment>
<![CDATA[
The following attributes are automatically added to the feed: <br />
<ul style="margin-left: 2em;">
<li><small>attribute_set_id</small></li>
<li><small>categories</small></li>
</ul>
]]>
</comment>
</field>
</group>
</section>
</system>
module.xml
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
<module name="Tatva_SLIFeed" setup_version="0.0.1">
<sequence>
<module name="SLI_Feed" />
</sequence>
</module>