Placement of the word "also"

Earlier today on another site in the network, a user posted a question like this:

Is there a better way to use [x]?

There was a lot more to it, but the very first comment addressed this question directly and explicitly:

Why do you want to use [x] and not [y]? Also have you considered using [z]?

I took this latter sentence as:

You should consider using [z] instead of [x].

And proceeded to explain why [z] is not a valid alternative to [x].

The commenter vehemently insists that it should be clear and obvious that by starting the sentence with "also," I should know that they actually meant:

You should consider using [z] in addition to [x].

Can someone please explain from an English and grammar standpoint why having "also" at the beginning of the sentence - with or without a comma - does not associate with the thoughts in that sentence the way he/she thinks that it does?

Solution 1:

"Also" when used in the beginning of a phrase is usually used to introduce a new point. (In any case "also" usually refers to the previous clause)

"Also, have you considered using [z]?" - here "also" is just used to introduce a new topic and the meaning is equivalent to "Why do you want to use [x] and not [y]? Have you considered using [z]?" Whether 'z' was meant to be used in addition or as a replacement to 'x', or to 'y', is unspecified.

Alternatives:

"Have you also considered using [z]?" = you should consider using [z] - again, whether [z] is an addition or a replacement and to what, [x] or [y], is not known.

"Have you considered also using [z]?" = you should consider using [z] as well as [y] or [x] - whether [z] is an addition to [x] or [y] is still unknown but in this case it is not a replacement

The question of whether [z] would be in addition/replacement to [x] or [y] might be obvious from context but not from the grammar:

"Why do you want to drink water and not tea? Also, have you considered drinking coffee?" - is coffee in addition or as a replacement? And to what, tea or water?