I don't think this is dangerous. I don't think you need to worry about it.
The affected files are just pairs of strings and the translated version for a particular language. The InfoPlist.strings file contains the file descriptions that appear in the Finder (and other places I assume) for the Document Types that Safari supports, for example "HTML document" and "CSS style sheet". The ServicesMenu.strings contains a similar short list of the Services provided by Safari, for example "Add to Reading List". The two files that are being flagged as modified are a bit boring as they are providing English translations for strings that are already in English. If you check the same files in another language folder within the Safari bundle, like for example French the concept is clearer.
<key>Web internet location</key>
<string>Adresse Internet du Web</string>
<key>Web site URL</key>
<string>Adresse URL du site web</string>
<key>Web site location</key>
<string>Adresse du site web</string>
<key>Windows icon image</key>
<string>Fenêtres icône image</string>
Within the thread discussing 1Password it doesn't appear that the modification was caused by 1Password. In fact it was initially suspected to be the reverse, the discussion in that thread was about whether the modifications were causing a problem with 1Password because someone was having trouble running it. In the end it turned out that the problem with 1Password was caused by Sophos. The modified Safari files had nothing to do with it.
For what it's worth I get the same errors when I run codesign against Safari on both my Macs. I tried reinstalling the latest OS X update (which includes Safari 7.0.5) but that made no difference. Even tried repairing permissions (which funnily enough did make one correction to a file in the Safari bundle) but unfortunately didn't resolve this issue.
Unless you have a problem running Safari or running extensions within Safari, I wouldn't worry about this.