[DON'T DO THIS! It will break things (see below).]

If it's just a matter of making the default priority "invisible", you can try setting org-priority-default to 32 (the ASCII code for SPACE):

(setq-default org-priority-default 32) 

That might break other things (e.g. trying to bump up the priority of a headline without a priority cookie using org-priority-up will signal an error). You can try to limit the damage by using setq-local in a buffer, so that only that buffer will see the breakage, but if you are dealing with multiple buffers (e.g. you want the agenda column view), then the setq-default is a blunt but more convenient instrument than using setq-local on each agenda file buffer.

Or you might not care about the org-priority-(up|down) breakage, but there might be other breakage as well - I don't know.

If you try it, reset org-priority-default to its default value to fix the breakage:

(setq-default org-priority-default 66) 

where 66 is the ASCII code for B.

In summary: caveat emptor and do this at your own peril. There is no warranty at all.

EDIT: You could probably advise org-columns (and/or org-agenda-columns) to do the default setting of org-priority-default before the call to the original function; and org-columns-quit to do the unsetting after the call to the original function. That way, when you activate column view, you don't get to see the default priority (and presumably, you don't try to set/change priorities: the underlying buffer in column view is read-only, but there are ways to modify properties and propagate them back I believe). Then when you exit column view, everything goes back to "normal". But I have not tested this and there are lots of things that could go wrong, I think.

[DON'T DO THIS! It will break things (see below).]

If it's just a matter of making the default priority "invisible", you can try setting org-priority-default to 32 (the ASCII code for SPACE):

(setq-default org-priority-default 32) 

That might break other things (e.g. trying to bump up the priority of a headline without a priority cookie using org-priority-up will signal an error). You can try to limit the damage by using setq-local in a buffer, so that only that buffer will see the breakage, but if you are dealing with multiple buffers (e.g. you want the agenda column view), then the setq-default is a blunt but more convenient instrument than using setq-local on each agenda file buffer.

Or you might not care about the org-priority-(up|down) breakage, but there might be other breakage as well - I don't know.

If you try it, reset org-priority-default to its default value to fix the breakage:

(setq-default org-priority-default 66) 

where 66 is the ASCII code for B.

In summary: caveat emptor and do this at your own peril. There is no warranty at all.

EDIT: You could probably advise org-columns (and/or org-agenda-columns) to do the default setting of org-priority-default before the call to the original function; and org-columns-quit to do the unsetting after the call to the original function. That way, when you activate column view, you don't get to see the default priority (and presumably, you don't try to set/change priorities: the underlying buffer in column view is (partially) read-only, but there are ways to modify properties and propagate them back I believe). Then when you exit column view, everything goes back to "normal". But I have not tested this and there are lots of things that could go wrong, I think.

[DON'T DO THIS! It will break things (see below).]

If it's just a matter of making the default priority "invisible", you can try setting org-priority-default to 32 (the ASCII code for SPACE):

(setq-default org-priority-default 32) 

That might break other things (e.g. trying to bump up the priority of a headline without a priority cookie using org-priority-up will signal an error). You can try to limit the damage by using setq-local in a buffer, so that only that buffer will see the breakage, but if you are dealing with multiple buffers (e.g. you want the agenda column view), then the setq-default is a blunt but more convenient instrument than using setq-local on each agenda file buffer.

Or you might not care about the org-priority-(up|down) breakage, but there might be other breakage as well - I don't know.

If you try it, reset org-priority-default to its default value to fix the breakage:

(setq-default org-priority-default 66) 

where 66 is the ASCII code for B.

In summary: caveat emptor and do this at your own peril. There is no warranty at all.

[DON'T DO THIS! It will break things (see below).]

If it's just a matter of making the default priority "invisible", you can try setting org-priority-default to 32 (the ASCII code for SPACE):

(setq-default org-priority-default 32) 

That might break other things (e.g. trying to bump up the priority of a headline without a priority cookie using org-priority-up will signal an error). You can try to limit the damage by using setq-local in a buffer, so that only that buffer will see the breakage, but if you are dealing with multiple buffers (e.g. you want the agenda column view), then the setq-default is a blunt but more convenient instrument than using setq-local on each agenda file buffer.

Or you might not care about the org-priority-(up|down) breakage, but there might be other breakage as well - I don't know.

If you try it, reset org-priority-default to its default value to fix the breakage:

(setq-default org-priority-default 66) 

where 66 is the ASCII code for B.

In summary: caveat emptor and do this at your own peril. There is no warranty at all.

EDIT: You could probably advise org-columns (and/or org-agenda-columns) to do the default setting of org-priority-default before the call to the original function; and org-columns-quit to do the unsetting after the call to the original function. That way, when you activate column view, you don't get to see the default priority (and presumably, you don't try to set/change priorities: the underlying buffer in column view is read-only, but there are ways to modify properties and propagate them back I believe). Then when you exit column view, everything goes back to "normal". But I have not tested this and there are lots of things that could go wrong, I think.