Shell Programming and Scripting

find does not read from stdin, and sed needs an input (filename as argument or stdin).
Your script is okay.
If you take a while read loop and quote the variables that holds filenames, then it is even takes filenames with special characters.

Code:

find ./ -type f \( -name "*.txt" -o -name "*.xml" \) |
while IFS= read -r f
do
  if ips=$(sed 's/#.*//' "$f" | grep -Eo '\b([0-9]{1,3}[.]){3}[0-9]{1,3}\b')
  then
    echo "File:$f"
    echo "$ips"
  fi
done

The if takes the exit status from the last command i.e. the grep (0 gives true).
One could as well test the variable of being non-null.
The quotes in echo "$ips" keep the newlines in the variable, while echo $ips would print them in a row (and the shell tries to glob them, but you have ensured it does not have special glob characters).