azurecurve

Appends a suffix (such as a copyright notice or link back) to the RSS feed.
This plugin is multi-site compatible; set a default at the network level which can be overridden for individual sites.
This plugin supports language translations. If you want to translate this plugin please sent the .po and .mo files to wordpress.translations@azurecurve.co.uk for inclusion in the next version (full credit will be given). The .pot fie is in the languages folder of the plugin and can also be downloaded from the plugin page on http://development.azurecurve.co.uk.

azurecurve RSS Suffix

Appends a suffix (such as a copyright notice or link back) to the RSS feed.

Ipstenu (Mika Epstein)

JohnnyWhite2007

Spam is one thing, but trolls and sock puppets are another. Sometimes people just decide they’re going to be jerks and create multiple accounts with which to harass your honest users. This plugin helps you fight back by logging the IP address used at the time of creation.
Log into your WP install as an Admin and you can look at their profile or the users table to see what it is. For security purposes a user’s own IP is not displayed to them when they look at their own profile.
<ul>
<li><a href="https://ko-fi.com/A236CEN/" rel="nofollow ugc">Donate</a></li>
</ul>
<h3>Privacy Notes</h3>
This plugin adds additional data to a new user’s <code>wp_usermeta</code> data under the <code>signup_ip</code> key. This data is directly tied to the user account, and is only editable via the database. Should a user account be deleted from the site, the data will be automatically deleted.
No external data is transmitted, it all stays on your install.

Register IPs

Does exactly waht it says

When a new user registers, their IP address is logged. Supports multisite and single site!

azurecurve RSS Suffix vs Register IPs