While in the progress of deploying signatures with centralized location in Office 365, I found this piece of code to be used.

Outlook - Remove Custom Signature.ps1

# Remove signures from users when you dont have centralized server 

$MSLocation =  $env:USERPROFILE.ToString() + "\AppData\Roaming\Microsoft\"
$SignaturesLocation =  $MSLocation + "Signatures"
$BackupFolder = $MSLocation + "Signatures Backup"


Try {
    
    "User profile location" + $SignaturesLocation
    cd $SignaturesLocation
    #New-Item -ItemType directory -Path $BackupFolder
    #Get-ChildItem -Path $SignaturesLocation + "\*.*" -Recurse | Move-Item -Destination @BackupFolder
    Get-ChildItem *.txt | Rename-Item -NewName { $_.name -Replace '\.txt$','.txt.bkp' }
    Get-ChildItem *.htm | Rename-Item -NewName { $_.name -Replace '\.htm$','.htm.bkp' }
    Get-ChildItem *.rtf | Rename-Item -NewName { $_.name -Replace '\.rtf$','.rtf.bkp' }

}
Catch [System.Exception] {
    
    Write-Host -ForegroundColor Red "Signature removal failed"
    Write-Host -ForegroundColor Green "This script only supports Windows Vista,Windows 7, Windows 8, Windows 8.1, or Windows 10"
    Write-Host -ForegroundColor Red "Your version of Windows is" ([System.Environment]::OSVersion.Version).ToString()
    $error[0].ToString() + $error[0].InvocationInfo.PositionMessage

}