I think that you are going to need better reasons than just being more friendly with other database clients by breaking a rule which is around for 20 years.
Well, that reason was enough for other sql clients to implement "\q" and "\quit" even if they don't use "\" commands.
Note that we are not breaking a rule, we already have "help" without slash and as I said, "slash way" still supported and still oficial way to exit.
For one, it seems to me that your patch is breaking multi-line SQL support with psql, as "quit" or "exit" are legit SQL object names.
No, it is not breaking. Did you test it? My patch takes care of multi-line commands. Look at second line of patch:
pset.cur_cmd_interactive && query_buf->len == 0
Line 4 also take care about other possible problems:
I know that this "feature" don't make any difference for most of you guys but also it will not hurt anyone and will help a little for newcomers and people that uses different sql clients. To be honest. I could understand that is not a good idea to accept patches like this if it is too big since it could make things hard to maintainers but honestly, this patch is very small and trivial.