Acceptance criteria

The user can select any text (word, phrase, sentence) and add a comment via the inline toolbar.
The user can click any focused block and add a comment to the whole block via the action strip.
Comment threads are anchored, they stay attached to their text or block even after edits nearby.
Multiple comments can exist on the same block without overlapping.
Comment counts are visible in the right margin without focusing the block.
Any user who joined the site can reply to a thread.

1.The user can select any text (word, phrase, sentence) and add a comment via the inline toolbar.

Reader

Editor

2. The user can click any focused block and add a comment to the whole block via the action strip.

Basic flow

Reader select word or phrase

User selects a word or phrase → inline toolbar appears → taps Comment
Thread panel opens on the right anchored to the selection → user types and submits
User selects a word or phrase → inline toolbar appears → taps link
Link is copy to be pasted (a confirmation tooltip appears)
User selects a word or phrase → inline toolbar appears → taps like (heart)
A new heart is added to the block text
User selects a word or phrase → inline toolbar appears → taps. 3 dots option
Contextual options list for reader appear

Reader or writer selects text block

User selects a text block → action trip appears → taps Comment
Thread panel opens on the right anchored to the selection → user types and submits
User selects a text block → action trip appears → taps link
Link is copy to be pasted (a confirmation tooltip appears)
User selects a text block → action trip appears → taps like (heart)
A new heart is added to the block text
User selects a text block → action trip appears → taps. 3 dots option
Contextual options list for reader or editor appear