All you're doing is bringing attention to the fact that they're chronically late. Note that this can come off as arrogant in and of itself.
Do not elaborate on the compliment; instead, take it at face value.
If you regularly praise your partner for their parenting, they may take it as a sign that you're surprised they're even trying.
Unfortunately, bringing this up does not provide any relief, but rather draws attention to how terrible their life is right now.
This "compliment" comes in a wide variety of sickening forms and is often used to imply racism or sexism.
Depending on the context, making comments about the appearance of a colleague, acquaintance, or stranger can be seen as harassing.
When you say someone looks great for their age, you are implying that they are not beautiful or handsome in and of themselves, but rather in comparison to crone.
Therefore, you are stating that they are not only depressed spinsters, but that something else is also keeping them that way.
It is never a good idea to compliment the appearance of a person's significant other, as it implies that you are comparing them to others.