Related Posts is permanently disabled if you edit settings via Customizer

[gravityrail]

Steps to reproduce the issue

1. On a fresh install (or with freshly-deleted jetpack_relatedposts options), enable the Related Posts module
2. Go into the customizer and edit Related Posts settings (e.g. disable show date)
3. Save

What I expected

Date is hidden

What happened instead

Related Posts is permanently disabled and there's no way to re-enable it!

Suggested solution

If we haven't enabled the UI which shows the "toggle" option for whether RP's are enabled, they should ALWAYS BE ENABLED since otherwise there's no way to switch them on.

Right now the only workaround is for users to implement something like this in an mu-plugin:

<?php

add_filter( 'jetpack_relatedposts_filter_allow_feature_toggle', 'enable_rp_feature_toggle' );

function enable_rp_feature_toggle( $val ) {
	return true;
}

and then manually re-enable RP's in the Reader settings every time they change a setting.

[richardmtl]

At least two more reports today:

3052392-t
3052572-t

[lezama]

great finding sir

[graylaurenm]

Worked for me! Thanks to Paul (ticket #3034557) for directing me here.

[aheckler]

3054180-t

[lschuyler]

3050277-t

[aheckler]

3087199-t