I am currently building an Asset Builder for Comment Assets.
Using the keyword %details-F_comment% renders
<textarea id="comment_0_comment" class="sq-form-field" style="width: 300px; height: 100px;" name="comment_0_comment"/>
Whilst I am happy with the text-area, whats the deal with the inline styling? 
Is there a tag I should be using to return clean form fields?
If there isn't it seems pretty bad to have to overwrite these inline styles with stronger external styles
The asset builder itself will also render <div id="page_asset_builder_330_type_comment" class="sq-asset-builder-tab-content" style="display: block;"> around itself.
This is extraneous as well, Is there any way to remove that?
[quote]I am currently building an Asset Builder for Comment Assets.
Using the keyword %details-F_comment% renders
<textarea id="comment_0_comment" class="sq-form-field" style="width: 300px; height: 100px;" name="comment_0_comment"/>
Whilst I am happy with the text-area, whats the deal with the inline styling?
Is there a tag I should be using to return clean form fields?
If there isn't it seems pretty bad to have to overwrite these inline styles with stronger external styles
The asset builder itself will also render <div id="page_asset_builder_330_type_comment" class="sq-asset-builder-tab-content" style="display: block;"> around itself.
This is extraneous as well, Is there any way to remove that?[/quote]
I don't think that there is any way that you can remove the inline styles without changing the Matrix code. And, any other CSS that you woudl add would not be more specific than the inline styles, those would override everything else. If I were you, I would just use put this into your code instead of the keyword if you are really worried about it:
Because as long as it is the same code (id and name) of what Matrix prints, it will still work, and get submitted correctly. So, you don't actually have to use the keyword (although it would always be best to).
If you are working on a client site, I would not use hard-coded content. Asset builder has broken code that like before during an upgrade because we do have to change IDs and names from time to time. Personal sites are fine because you often know exactly what you have done, but this has caused problems on large and/or complex sites before.
And no, there is no way to remove the inline styles. All form fields are specific based on the cotent type and there are no type-specific stylesheets in the system. It's just part of the overall design associated with bringing backend components into the frontend via simple edit and asset builder.
Ok, new and more upgrade friendly solution. Use javascript to remove the style attribute. 
I think you may be able to override it with an external style sheet rule.
Element styles have the same specificity as a single ID, so in theory a rule with a specificity of 200 or higher would over-ride it.
Try wrapping the elements you want control of in another div, then do this:
#some-outer-div-id #build-wrapper-id the-element-to-over-ride{ the rules to override}
Richard