Сколько ни читай этот текст, смысл всё равно остаётся неясным.

This is a very common Russian concessive pattern:

сколько ни + verb = no matter how much / however much ...

So:

• Сколько ни читай этот текст...
  = No matter how much you read this text...

The idea is that the result in the main clause does not change, even if the action is repeated a lot.

Russian uses similar patterns with other question words too:

• как ни старайся = no matter how hard you try
• где ни ищи = no matter where you look
• что ни говори = whatever you say / no matter what you say

So here сколько does not ask a real question. It introduces a pattern meaning however much.

Yes, it is the imperative form, but in this construction it is not a literal command.

Here, the imperative is used in a more general, idiomatic way. It often gives the sense of:

• even if you do it repeatedly
• however much one may do it
• do it as much as you like, the result is the same

So читай here is not somebody ordering another person to read. It is closer to a generalized you:

• Сколько ни читай...
  = No matter how much you read...

This use of the imperative is very common in Russian in fixed concessive expressions.

Because ни is the particle normally used in this kind of concessive pattern.

Compare the roles:

• не = ordinary negation
• ни = often used with words like кто, что, где, как, сколько in patterns meaning no matter..., whoever..., whatever...

So:

• Сколько ни читай... = No matter how much you read...

If you replaced ни with не, the sentence would no longer have the same standard meaning or sound natural in this pattern.

A useful rule of thumb: after words like кто, что, как, где, сколько, when Russian means no matter who/what/how/where/how much, it often uses ни.

Yes, but only in a general sense.

Russian often uses the 2nd person singular form to mean something like:

• you in general
• one
• anyone

So читай here does not necessarily mean one specific person is being addressed. It means something like:

• however much you read
• however much one reads

English also does something similar with you:

• You can try all day, but it won’t help.

That does not always mean one specific person; it can mean people in general.

Всё равно means something like:

• all the same
• anyway
• still
• nevertheless

In this sentence it emphasizes that the result does not change:

• смысл всё равно остаётся неясным
  = the meaning still remains unclear / is unclear anyway

Without всё равно, the sentence would still make sense:

• Сколько ни читай этот текст, смысл остаётся неясным.

But всё равно makes the contrast stronger: even after all that reading, the meaning is still unclear.

It actually is in the accusative, but for an inanimate masculine noun, the accusative looks the same as the nominative.

• nominative: этот текст
• accusative: этот текст

The verb читать takes a direct object, so text must be in the accusative case.

Because текст is:

• masculine
• singular
• inanimate

its accusative form is identical to its nominative form.

Compare with an animate masculine noun, where the form would change:

• Я вижу этого человека.
  accusative looks like genitive because человек is animate

But with текст, no visible change happens.

Because смысл is the subject of the main clause:

• смысл всё равно остаётся неясным

Here, the thing that remains unclear is смысл.

So the structure is:

• subordinate clause: Сколько ни читай этот текст
• main clause: смысл всё равно остаётся неясным

In the main clause:

• смысл = subject, so nominative
• остаётся = verb
• неясным = predicative complement

Because after verbs like оставаться / остаться (to remain), Russian often uses the instrumental case for the word describing the resulting or continuing state.

So:

• остаётся неясным = remains unclear

This is a very standard pattern:

• Он остался довольным. = He remained satisfied.
• Город остаётся важным центром. = The city remains an important center.
• Вопрос остаётся открытым. = The question remains open.

You may also see short forms with some verbs in Russian, but with оставаться the instrumental is very common and natural.

So неясным is not just an adjective form chosen randomly; it is the adjective неясный in the instrumental singular masculine, agreeing with смысл.

The imperfective is natural here because the idea is:

• repeated reading
• ongoing effort
• reading as a process

So читай fits the meaning however much you keep reading / however many times you read.

In this sentence, the focus is not on finishing the reading once, but on the repeated attempt to understand the text.

Also, the main verb остаётся is imperfective because it describes a continuing state:

• the meaning remains unclear

So both parts of the sentence match well:

• repeated/processual action: читай
• continuing state: остаётся

Because the sentence has two clauses:

1. Сколько ни читай этот текст
2. смысл всё равно остаётся неясным

The first clause is a subordinate concessive clause, and the second is the main clause. Russian normally separates them with a comma.

So the comma marks the boundary between:

• no matter how much you read this text
• the meaning still remains unclear

Yes. Russian word order is flexible, although not completely free.

The given order is very natural:

• Сколько ни читай этот текст, смысл всё равно остаётся неясным.

It presents:

1. the unsuccessful effort
2. the unchanged result

You could move things around for emphasis, for example:

• Смысл всё равно остаётся неясным, сколько ни читай этот текст.

That is also understandable, but the original version sounds especially natural because it sets up the concession first and then gives the result.

It is basically neutral standard Russian.

Nothing in it is slangy or highly literary. The pattern сколько ни читай is normal educated Russian and is common both in writing and speech.

The sentence sounds a little thoughtful or analytical because of words like:

• смысл
• остаётся неясным

But grammatically and stylistically, it is not unusual or overly formal.