[straube]

We play 1M-3C as natural invitational so 1M-1N, 2M-3C is natural and less than invitational....and seems to hardly ever come up.

For those using 1M-3C as fit-showing or Bergen etc, keeping 3C as natural probably makes sense.

For us, I've wondered if 1M-1N, 2M-3C should show a fit for partner's suit. As would probably 1M-1N, 2M-3M. So one would
be stronger than the other. Constructive vs invitational. I know many use 1H-1N, 2H-2S as artificial and possibly a raise. I'm thinking more
of 1S-1N, 2S

Could even do 3C as both minors and 3D as the second raise. I don't think I like this as much.

Good or bad idea?

[Kungsgeten]

We play 2NT as forcing after 1M-1NT; 2M. 2NT is basically a hand wanting to sign off in 3m, or invitational with 2-card support (Lebensohl kind of). A direct raise to 3M is a limit raise with 3 card support (we play forcing 1NT) and a direct 3m is invitational (but you could use it as fit showing).