" and will crack the grout and lead to leaks "

Grout is not nor was ever intended to be waterproof. That is why the Hardie board or any cement board gets a topical waterproofing applied.

" Caulk is notorious for molding so I can't see using caulk in corners "

Not with a proper fan and running it regularly and for enough time after showering.

" If it's so sure the grout will fail/crack in areas so that we use a sealer on the hardi-backer before the tile is installed over it, "

Again, grout was never intended to be waterproof and the backer is designed to be the drainage plain, which is why that is where the waterproofing is, behind the tile..

A correctly waterproofed shower can be showered in, without tile. Tile is merely the decorative surface cladding. Just like any other cladding. If mold is an issue, the waterproofing or the ventilation is the culprit. Not the grout or the caulk. Panelized systems also use caulk at joins, which can mold. Again, the culprit is waterproofing or ventilstion. Not the panels. Not the tile.

Thank you for the comments....and Millworkman, I think you made the comment that I copied over here to get more input on so I appreciate the information in the first place...and for your added comment here. I had not run across the need to caulk corners but I have been dragging my feet the whole way through doing tile instead of a different, less troublesome material.

It just seems to me that the grout industry is pushing several lies... or perhaps, more likely, I'm still under educated! So the only reason we seal grout is so the grout won't mold or discolor and it has nothing to do with keeping water from getting behind the tile? Same comment with respect to grouts like Mapei Plus FA, which I am using?

I am also doing more do-it-yourself drywall work and as I work I keep being "floored" that we are still using drywall products that are EXPECTED to crack with time and small movements of the home. We put men on the moon but we haven't developed flexible drywall mud....or tile grout. In the case of the drywall, there is just a crack but in a shower, sometimes things behind the tile are bound to remain damp/wet for extended periods and that just boggles my mind. I should have less trouble than most because I dry my shower with my towel after I dry myself. Those shower floors with the tiny ceramic squares and lots of grout.....the concept of water full on the floor, seeping between the tiny imperfections in the grout and dampening the thinset over time.....that just sounds like a recipe for failure no matter how well the backer is sealed.

I guess I'm sounding awfully pessimistic but the concept just seems counter to my "keep everything dry" mindset. I seriously considered going with a sheet vinyl covered shower....one piece for the ceiling and one piece wrapped around the three walls.....most of the fiberglass/acrylic surrounds seemed pretty expensive for their super boring colors/styles and they still had gaps I thought would pool water after each shower.

"That is why the Hardie board or any cement board gets a topical waterproofing applied."

"any" is the problem qualifier here. GoBoard and other modern "cement" boards are waterproof, not water-resistant, eliminating the extra time and expense of secondary waterproofing.

"Waterproof Built-in Seal only the board joints and fastener penetrations for a waterproof tile assembly per GoBoard installation instructions."

Yes @Joseph Corlett LLC I should have been more clear. Hardie Board definitely needs a topical waterproofing and the traditional cement boards as well however there are waterproof products, Go Board being one, that do not require waterproofing.

" So the only reason we seal grout is so the grout won't mold or discolor and it has nothing to do with keeping water from getting behind the tile "

Correct, and in actuality it will still stain, the sealant just helps slow it down. And in reality does nothing for mold.

Epoxy grout

Really appreciate the comments/clarification. Thankfully, before I started tiling the shower, I ran across some detail somewhere about the need to seal the Hardibacker. I knew one had to be careful tiling a bath but I'm still in shock that it's a given that the grout will fail. So...thanks for helping further my tile education. Most of my prior tile work was flooring but did some wainscot in a previous bath and also doing wainscot in the present bath...and doing the shower in tile.

My previous home already had a very nice one-piece fiberglass Kohler shower...ceiling and everything...one piece. I like that concept a lot but they are pretty much impossible to get in a remodel without taking out some wall.

Even above that one-piece Kohler unit, this is by far my favorite shower.....outside where the humidity is no problem, you can power wash the walls if you like, or just slosh some bleach water in there now and then, and you don't track dirt in the house if you were doing some extra dirty yard work.

Cinder block interior, lime block exterior, aluminum carport materials repurposed as trusses to support the glass ceiling (tempered shower door glass), hot and cold water via PEX underground from the house.

My previous home already had a very nice one-piece fiberglass Kohler shower...ceiling and everything...one piece.

Those one-piece items are considered "cheap", but we had them in our first house, and we've never had anything else as functional: So easy to clean, no corners to give problems, no grout.

Thanks for the note on the one-piece shower. The one I had was very spacious...seat in two corners and a light overhead. I'm sure it was installed during the original build as it wouldn't have fit in any doorway. 'Course, if one ever fails, it will take a saw to get the thing out!

Very difficult to get a good photo but I had one for the real estate photos:

There is a reason that shower shoes are recommended in concrete block jail house showers. Concrete is highly porous and holds on to moisture and nasties.

Duly noted, seems like I have heard the same about cast iron skillets.

I had a non-slip fiberglass grid (look for the yellow corner in the second photo) on my shower floor to elevate my feet off the surface.

The alternative — acrylic is ugly

I couldn't agree more. The acrylic panels are simply boring and cost way too much for that level of boredom!

I have been ridiculed many years in the past for this but it worked very nicely....but took some care in installation to round the shower backerboard corners to prevent a sharp crease. Sheet vinyl comes in LOTS of patterns now and is very waterproof now as compared to the old linoleum which was not so good in wet places. I used sheet vinyl in a mobile home garden tub/shower surround remodel. It looked very nice, never leaked, and shed water like a duck's back. Some shower surround company needs to take that concept and make something more appealing than the white acrylic stuff.