I believe that while the bag and rod would be locked in place, an Immovable Rod halfway into a Bag of Holding will still deactivate or be moved with enough weight or force. That includes any weight in excess of 8,000 lbs. (4 tons) or a DC 30 Strength check. Note that the effects of extreme weight and extreme strength on an Immovable Rod are different.
The text of Immovable Rod is:
This flat iron rod has a button on one end. You can use an action to press the button, which causes the rod to become magically fixed in place. Until you or another creature uses an action to push the button again, the rod doesn't move, even if it is defying gravity. The rod can hold up to 8,000 pounds of weight. More weight causes the rod to deactivate and fall. A creature can use an action to make a DC30 Strength check, moving the fixed rod up to 10 feet on a success.
If more than 8,000 lbs is placed on the Immovable Rod, even if it's placed halfway in a Bag of Holding, it deactivates and the rod and bag fall. A strength check could have multiple results. A creature can pull the rod from the bag (causing the bag to fall off), push it further into the bag (leaving it in the bag's pocket dimension, meaning the bag will fall), or push the rod and the bag 10 feet (the rod stays halfway in the bag). Also consider that weight put on the button could cause it to shut off immediately, even if it's less than 8,000 lbs.
Up to that point, however, I would rule that any force placed on the rod is no different with or without the Bag of Holding. Even placing a ton of weight (2,000 lbs) on the rod shouldn't puncture or break the bag, as the rod is fixed in space and supports the weight entirely. However, I wouldn't say there's any benefit in terms of stability gained by attaching a Bag of Holding to one end, and neither does the linked answer. It simply says that attempting to move an active Immovable Rod into a dimensional space in a Bag of Holding would require a strength check to do, as it's considered to be moving the rod.
Keep in mind that the linked answer is not written rule, merely an interpretation of the effects of an Immovable Rod, the pocket dimensional space of a Bag of Holding, and the nature of physics in the D&D system. It does not override the rules of an Immovable Rod, unless the DM decrees it so.