[bodyfour]

I sort of agree that there isn't any strong reason for an interactive shell to have 100% bash compatibility. However, when I tried to convert to using fish I found my muscle-memory used too many simple history substitutions like "!!" and "!$" (which actually pre-date bash; they arrived with csh 40 years ago!) which were missing. Ultimately I gave up and went back to bash.

It sort of is an "uncanny valley" for a text interface. It feels close enough to a traditional UNIX shell that I start to interact with it like one... but has enough differences that I found myself constantly tripping over them.

[djsumdog]

It was difficult to implement !! and !$ in fish (I rarely actually used them in bash, so it wasn't an issue for me) and I know others who found that annoying. However if you dig around, there are a couple of solutions on Stack Overflow and blog posts that add in that functionality using plugins or functions. It's not exactly the same, but some of them work pretty well.

[claar]

You may be underestimating the importance of these particular operators to experienced users. I at least would be very dissuaded from trying an alternate shell without a simple way to enable these.

[askz]

I use !! maybe ten times per day. !$ can be implemented in your PS1 easily.

[ViViDboarder]

I used to. Now I just Ctrl-P.